docs: split LLM project workflow into task-specific modes (Closes #333)

Consolidate all four canonical workflow files and router SKILL.md:
- review-merge-pr.md (from #334 canonical prompt)
- reconcile-landed-pr.md (reconciliation gates + handoff schema)
- create-issue.md (canonical issue-creation prompt)
- work-issue.md (canonical author/coder prompt)

SKILL.md is now a short router with mode isolation and universal rules.
Adds final-report schemas for all modes and 13 doc-contract tests.

Supersedes partial split work in PR #335; full #333 acceptance in one PR.

skills/llm-project-workflow/schemas/create-issue-final-report.md

@@ -0,0 +1,46 @@
+# Create-issue controller handoff schema
+
+**Task mode:** `create-issue`
+
+End every create-issue run with a section titled exactly `Controller Handoff`.
+Use this canonical field set. Do not omit fields — use `none` or
+`not verified in this session` where appropriate.
+
+Do not use legacy fields: `Workspace mutations`, `Mutations: None` (when
+mutations occurred).
+
+```md
+## Controller Handoff
+
+- Task:
+- Repo:
+- Role:
+- Identity:
+- Active profile:
+- Runtime context:
+- Requested issue task:
+- Workflow source:
+- Capability proof:
+- Duplicate search terms:
+- Duplicate search pagination proof:
+- Duplicates found:
+- Issues created:
+- Issues commented:
+- Issues edited:
+- Issues skipped as duplicates:
+- Labels/assignees/milestones changed:
+- File edits by issue creator:
+- Worktree/index mutations:
+- Git ref mutations:
+- MCP/Gitea mutations:
+- Issue mutations:
+- Label/assignment/milestone mutations:
+- External-state mutations:
+- Read-only diagnostics:
+- Blockers:
+- Current status:
+- Safe next action:
+- Safety statement:
+```
+
+Identity format: `username / profile` (not personal email unless required — #305).