feat: add WebVTT context generation to chat WebSocket endpoint

- Import topics_to_webvtt_named and recordings controller
- Add _get_is_multitrack helper function
- Generate WebVTT context on WebSocket connection
- Add get_context message type to retrieve WebVTT
- Maintain backward compatibility with echo for other messages
- Add test fixture and test for WebVTT context generation

Implements task fn-1.2: WebVTT context generation for transcript chat

scripts/ralph/prompt_plan.md

@@ -0,0 +1,58 @@
+You are running one Ralph plan gate iteration.
+
+Inputs:
+- EPIC_ID={{EPIC_ID}}
+- PLAN_REVIEW={{PLAN_REVIEW}}
+- REQUIRE_PLAN_REVIEW={{REQUIRE_PLAN_REVIEW}}
+
+Steps:
+1) Re-anchor:
+   - scripts/ralph/flowctl show {{EPIC_ID}} --json
+   - scripts/ralph/flowctl cat {{EPIC_ID}}
+   - git status
+   - git log -10 --oneline
+
+Ralph mode rules (must follow):
+- If PLAN_REVIEW=rp: use `flowctl rp` wrappers (setup-review, select-add, prompt-get, chat-send).
+- If PLAN_REVIEW=codex: use `flowctl codex` wrappers (plan-review with --receipt).
+- Write receipt via bash heredoc (no Write tool) if `REVIEW_RECEIPT_PATH` set.
+- If any rule is violated, output `<promise>RETRY</promise>` and stop.
+
+2) Plan review gate:
+   - If PLAN_REVIEW=rp: run `/flow-next:plan-review {{EPIC_ID}} --review=rp`
+   - If PLAN_REVIEW=codex: run `/flow-next:plan-review {{EPIC_ID}} --review=codex`
+   - If PLAN_REVIEW=export: run `/flow-next:plan-review {{EPIC_ID}} --review=export`
+   - If PLAN_REVIEW=none:
+     - If REQUIRE_PLAN_REVIEW=1: output `<promise>RETRY</promise>` and stop.
+     - Else: set ship and stop:
+       `scripts/ralph/flowctl epic set-plan-review-status {{EPIC_ID}} --status ship --json`
+
+3) The skill will loop internally until `<verdict>SHIP</verdict>`:
+   - First review uses `--new-chat`
+   - If NEEDS_WORK: skill fixes plan, re-reviews in SAME chat (no --new-chat)
+   - Repeats until SHIP
+   - Only returns to Ralph after SHIP or MAJOR_RETHINK
+
+4) IMMEDIATELY after SHIP verdict, write receipt (for rp mode):
+   ```bash
+   mkdir -p "$(dirname '{{REVIEW_RECEIPT_PATH}}')"
+   ts="$(date -u +%Y-%m-%dT%H:%M:%SZ)"
+   cat > '{{REVIEW_RECEIPT_PATH}}' <<EOF
+   {"type":"plan_review","id":"{{EPIC_ID}}","mode":"rp","timestamp":"$ts"}
+   EOF
+   ```
+   For codex mode, receipt is written automatically by `flowctl codex plan-review --receipt`.
+   **CRITICAL: Copy EXACTLY. The `"id":"{{EPIC_ID}}"` field is REQUIRED.**
+   Missing id = verification fails = forced retry.
+
+5) After SHIP:
+   - `scripts/ralph/flowctl epic set-plan-review-status {{EPIC_ID}} --status ship --json`
+   - stop (do NOT output promise tag)
+
+6) If MAJOR_RETHINK (rare):
+   - `scripts/ralph/flowctl epic set-plan-review-status {{EPIC_ID}} --status needs_work --json`
+   - output `<promise>FAIL</promise>` and stop
+
+7) On hard failure, output `<promise>FAIL</promise>` and stop.
+
+Do NOT output `<promise>COMPLETE</promise>` in this prompt.