feat: wire librarian as the primary agent for documentation and instruction file maintenance

Expand librarian role to own cross-tool instruction file sync,
.memory/ file maintenance, and knowledge merge workflows. Lead
now proactively dispatches librarian in PHASE-WRAP and Documentation
Completion Gate instead of handling docs inline.

.config/opencode/commands/save-memory.md

@@ -55,19 +55,20 @@ Example cross-reference:
 Re-read updated `.memory/` files to confirm they reflect current understanding.
 Report what was added/updated and where.
 
-## Step 6: Sync cross-tool instruction files when project knowledge changed
+## Step 6: Delegate instruction file sync to librarian
 
-Check whether `.memory/knowledge.md` was **materially** updated in this save.
-Material updates include project-level changes such as architecture, conventions,
-or build/test/lint commands.
+If `.memory/knowledge.md` was **materially** updated in this save (architecture,
+conventions, commands — not just plans/research), dispatch the `librarian`
+subagent to:
 
-- If there was a material `knowledge.md` update:
-  - Read current instruction files: `AGENTS.md`, `CLAUDE.md`,
-    `.github/copilot-instructions.md`, `.cursorrules`
-  - Update them to reflect the new core project knowledge while preserving
-    tool-specific formatting and project-specific content.
-- If updates were only plans/research/tracking details (no project-level
-  knowledge change), do **not** update instruction files.
+1. Read all cross-tool instruction files (`AGENTS.md`, `CLAUDE.md`,
+   `.github/copilot-instructions.md`, `.cursorrules`)
+2. Check for knowledge in instruction files not yet in `.memory/knowledge.md`
+   and merge it inward
+3. Update instruction files to reflect new `.memory/knowledge.md` content
+4. Report sync status
+
+If updates were only plans/research/tracking details, skip this step.
 
 ## Guidelines