docmontage: make music + end-tag mandatory, add Remotion EndTag component

User override during the audit runs made music and an end-tag MANDATORY
defaults for documentary-montage (narration stays optional). This commit
codifies those defaults into the pipeline manifest + director skills and
ships the Remotion end-tag component that the compose stage now
concatenates after the FFmpeg body.

Changes:

- pipeline_defs/documentary-montage.yaml: idea/edit/compose stages now
  require music_plan and end_tag_plan to be present; opt-out requires
  an explicit user note recorded in metadata.

- skills/pipelines/documentary-montage/idea-director.md: rewrote sections
  4 (music MANDATORY), 5 (end-tag MANDATORY with shape
  {text,palette,duration_seconds,render_engine:remotion,component:EndTag}),
  6 (narration OPTIONAL), 7 (updated brief JSON shape), 8 (quality gate).
  Common Pitfalls grew two entries covering silent-contract drift and
  end-tag omission.

- skills/pipelines/documentary-montage/compose-director.md: section 4
  now stops on music-contract violation; new section 4b documents the
  two-engine flow (FFmpeg body -> npx remotion render EndTag -> ffmpeg
  concat). Quality gate checks render_report.metadata.music_mixed and
  end_tag_rendered.

- remotion-composer/src/components/EndTag.tsx (new): bold uppercase
  typographic end-card with animated 0->100% underline draw-in and a
  single left-to-right shimmer sweep. Supports cool_offwhite_on_black
  and warm_ivory_on_black palettes. Renders at 1920x1080 @ 30fps.

- remotion-composer/src/Root.tsx: register EndTag as a first-class
  composition (durationInFrames=165, 5.5s hold) so it can be rendered
  standalone via the Remotion CLI with --props overrides.

skills/pipelines/documentary-montage/compose-director.md

@@ -131,8 +131,60 @@ and L-cut sfx layers. Your job is to execute them faithfully:
 - L-cut SFX layers = mix at 0.5-0.7 volume, under music.
 - No narration unless explicitly present in `edit_decisions.audio.narration`.
 
+**Music is MANDATORY.** If the edit has no music entry, check the brief:
+
+- `brief.metadata.music_plan.source == "none"` with an `opt_out_reason` →
+  the user explicitly opted out. Render silent and note it in
+  `render_report.warnings`.
+- Anything else → STOP. This is a contract violation. Surface it to
+  the user before rendering. A silent render on a music-mandatory brief
+  is the loudest failure mode in this pipeline.
+
+Do NOT add ambient noise "to fill the gap".
+
+### 4b. Render The End-Tag Via Remotion, Concatenate After Body
+
+The end-tag is rendered **separately** from the FFmpeg body and
+concatenated at the tail. This is deliberate — it sidesteps the
+`video_compose.render` scene-adapter mismatch and keeps the two
+render engines (FFmpeg for footage, Remotion for typography) cleanly
+separated.
+
+Read `brief.metadata.end_tag_plan`:
+
+```json
+{
+  "text": "WE BUILT BOTH WITH THE SAME HANDS.",
+  "palette": "warm_ivory_on_black",
+  "duration_seconds": 5.5,
+  "render_engine": "remotion",
+  "component": "EndTag"
+}
+```
+
+Execution path:
+
+1. Compose the body via FFmpeg (cuts + LUT + music + silence window).
+   Save as `projects/<name>/renders/body.mp4`.
+2. Render the end-tag via Remotion CLI with component-specific props:
+   `npx remotion render EndTag --props='{"text":"...", "palette":"...","durationInFrames":132}' projects/<name>/renders/end_tag.mp4`
+   (5.5s at 24fps = 132 frames). Canvas must match body canvas.
+3. Concat body + end_tag with `ffmpeg -f concat -safe 0 -i list.txt -c copy final.mp4`
+   or, if encoders don't match, re-encode with the documentary spec.
+
+**End-tag is MANDATORY.** The ONLY way to skip it is an explicit user
+opt-out recorded as `end_tag_plan: null` with an `end_tag_opt_out_reason`.
+If the brief has an end-tag plan but you skipped rendering it, that is
+a contract violation. Stop and surface before finalizing.
+
+Record in `render_report`:
+- `end_tag_rendered: true | false`
+- `end_tag_path: "projects/<name>/renders/end_tag.mp4"`
+- `end_tag_text: "..."` (for audit trail)
+
 If the brief says "no music" and the edit correctly has no music
-entry, render silent. Do NOT add ambient noise "to fill the gap".
+entry AND `music_plan.source == "none"` with an opt-out reason, render
+silent. Do NOT add ambient noise "to fill the gap".
 
 ### 5. Render At Documentary Spec
 
@@ -208,14 +260,16 @@ Record verifications in `render_report.verification_notes`.
 ### 8. Quality Gate
 
 - Output file exists and plays.
-- Duration within ±1s of `brief.duration_seconds`.
+- Duration within ±1s of `brief.duration_seconds` (body + end-tag inclusive).
 - Resolution matches `target_platform` canvas.
 - LUT was applied (or a warning logged).
-- Music is present iff the brief planned for it.
+- **Music is present** unless `brief.metadata.music_plan.source == "none"` with an explicit opt-out reason.
+- **End-tag MP4 was rendered and concatenated** unless `brief.metadata.end_tag_plan` is null with an explicit opt-out reason. Last frame of final MP4 must be the end-tag card in that case.
 - First and last frames verified.
 - Silence window (if any) verified in the waveform.
 - No narration unless brief-approved.
 - `render_report.warnings` lists every substitution.
+- `render_report.metadata.music_mixed = true` and `render_report.metadata.end_tag_rendered = true` (or explicit opt-out recorded).
 
 ## Common Pitfalls
 

skills/pipelines/documentary-montage/idea-director.md

@@ -71,19 +71,60 @@ Shape options:
 - **list/catalogue** — "everyone who..." structure, no arc, just
   accumulation (good for reverent or elegiac)
 
-### 4. Note Music Intent
+### 4. Note Music Intent (MANDATORY)
 
-Documentary montage is inseparable from its music bed. Decide now:
+Documentary montage is inseparable from its music bed. **Music is MANDATORY
+for this pipeline.** The ONLY way out is an explicit user opt-out (e.g.
+"no music, I want it silent") — which MUST be recorded as
+`music_plan.source = "none"` with a `music_plan.opt_out_reason` field.
+
+Silent-by-design briefs that feel "pure" at the idea stage regularly look
+like abandoned footage at compose time. Do not assume silence will earn
+itself. If the user has not mentioned music, ASSUME THEY WANT IT and pick:
 
 - user-provided track (put path in `music_plan.source_path`),
 - music library pick (list what's in `music_library/`),
-- generated (name the tool and prompt seed),
-- or none (silence).
+- generated (name the tool and prompt seed with register),
+- explicit opt-out (`source: "none"` + `opt_out_reason`).
 
 **Warn the user if no music source is available.** Do not silently
 defer this — it becomes an expensive surprise at the asset stage.
 
-### 5. Record The Brief
+### 5. Note End-Tag Intent (MANDATORY)
+
+Every documentary-montage film closes on a philosophical end-tag — one
+short, abstract line that gives the whole thing meaning. It is rendered
+as a Remotion end-card ("shining underlined tag" register — bold weight,
+letter-spaced, animated underline) and concatenated after the last clip.
+
+**End-tag is MANDATORY.** The ONLY way out is an explicit user opt-out
+recorded as `end_tag_plan: null` with an `end_tag_opt_out_reason` field.
+
+Propose the end-tag at the brief stage. Write 3 options and recommend one.
+Expected shape:
+
+```json
+{
+  "end_tag_plan": {
+    "text": "WE BUILT BOTH WITH THE SAME HANDS.",
+    "palette": "warm_ivory_on_black",
+    "duration_seconds": 5.5,
+    "render_engine": "remotion",
+    "component": "EndTag"
+  }
+}
+```
+
+Keep the copy to 3-9 words. It must be a thesis, not a summary.
+
+### 6. Note Narration Intent (OPTIONAL)
+
+Unlike music and end-tag, narration is OPTIONAL. Absence is fine if
+visuals + music + end-tag carry the register. If narration IS used, name
+the TTS provider and voice. Record `narration: "none"` explicitly if
+there's no narration — don't leave the field missing.
+
+### 7. Record The Brief
 
 Minimum fields the brief must carry:
 
@@ -97,7 +138,18 @@ Minimum fields the brief must carry:
   "sources_allowed": ["pexels", "archive_org", "nasa"],
   "generated_clips_allowed": false,
   "narration": "none",
-  "music_plan": { "source": "library", "path": "music_library/dawn_04.mp3" },
+  "music_plan": {
+    "source": "generated",
+    "provider": "elevenlabs",
+    "prompt_seed": "slow ambient drone in A minor, no percussion, 60s sustained swell, Max Richter register"
+  },
+  "end_tag_plan": {
+    "text": "THE CITY KEEPS ITS OWN VIGIL.",
+    "palette": "cool_offwhite_on_black",
+    "duration_seconds": 5.5,
+    "render_engine": "remotion",
+    "component": "EndTag"
+  },
   "era_mix": "any",
   "target_platform": "social_short"
 }
@@ -107,12 +159,15 @@ Minimum fields the brief must carry:
 Pexels, "vintage" biases toward Archive.org Prelinger, "any" leaves it
 open for the scene director to decide per slot.
 
-### 6. Quality Gate
+### 8. Quality Gate
 
 - Thematic question is ONE sentence.
 - Tone is ONE register from the fixed list.
 - Duration and shape are concrete numbers / enum values.
-- Music source is named OR the brief explicitly says "no music".
+- `music_plan` is present AND either names a real source OR has
+  `source: "none"` + `opt_out_reason` (explicit user decision).
+- `end_tag_plan` is present AND either has a non-empty `text` OR is
+  `null` with `end_tag_opt_out_reason` (explicit user decision).
 - Sources list is non-empty and at least one requested source is
   `available` per `corpus_builder.source_provider_menu` surfaced in
   preflight.
@@ -125,3 +180,7 @@ open for the scene director to decide per slot.
 - Ignoring duration. A 45s piece with 50 cuts is nausea. A 3-minute
   piece with 12 cuts is a slideshow.
 - Forgetting to ask about music. The user usually has an opinion.
+- Assuming silence will earn itself. It won't. Music is mandatory unless
+  the user explicitly says no.
+- Skipping the end-tag because "the images speak for themselves". They
+  don't — the end-tag is the thesis. Propose one every time.