feat(meta): replace sprint workflow with kanban + milestones (D-221)

Sprint-based workflow (38 sprints) replaced by kanban + milestones.
Milestones are many-to-many with tickets and can block each other.

New: /whats-next skill (dependency-driven batch selection with Si
refinement review), /pr-process skill (renamed from pr-push, adds
review comment pickup), clerk agent + pre-push hook for D-record
consistency checks.

Deleted: sprint CLI, sprint-start/sprint-plan/sprint-status skills,
team-scoped file restrictions. Si rewritten as refinement manager.
All 19 agent briefings updated from stale PROJECT_STATE.md reference
to live ticket milestone queries.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude/rules/project-structure.md

@@ -21,15 +21,14 @@ docs/
   architecture/       # Technical architecture documents
   design/             # Game design documents
   diagrams/           # d2 source + PNG renders
-  sprints/            # Sprint briefings per team
+  sprints/            # Historical archive (Sprint 1–38) — no new sprint directories
   workshops/          # Workshop briefs and outputs
 db/
   schema.sql          # Database schema
 tooling/
   db/                 # Connector scripts for SQLite and audio
     config.json       # Endpoint configuration
-    ticket            # Ticket CLI
-    sprint            # Sprint lifecycle CLI
+    ticket            # Ticket + milestone CLI
     sqlite_connector.py   # SQLite mini MCP
     audio_connector.py    # Stable Audio Open connector
 .claude/

.claude/rules/team-patterns.md

@@ -3,7 +3,7 @@
 ## Model selection
 
 Default model is Opus 4.6 (200K context). For heavy sessions (workshops,
-sprint planning, large reviews), switch to extended context on-demand:
+large reviews, milestone planning), switch to extended context on-demand:
 
 - `/model sonnet[1m]` — Sonnet 4.6 with 1M context window
 - `/model opus[1m]` — Opus 4.6 with 1M context window
@@ -20,7 +20,7 @@ Key: writers use Write tool directly (no transcription bottleneck), librarian ca
 
 ## Team monitoring (stuck agent detection)
 
-When leading a team (sprint, workshop, or any multi-agent session):
+When leading a team (workshop, batch, or any multi-agent session):
 
 **Agent heartbeat rule** — include in every agent spawn prompt:
 > If you have been working on a single task for more than 15 minutes

.claude/rules/ticket-cli.md

@@ -25,10 +25,27 @@ tooling/db/ticket create <type> <title> [--parent N] [--priority P] [--decision
 
 # Read
 tooling/db/ticket show <id>
-tooling/db/ticket list [--sprint N] [--team T] [--status S]
+tooling/db/ticket list [--milestone N] [--team T] [--status S]
 
 # Update
 tooling/db/ticket assign <id> <agent>
+
+# Dependencies
+tooling/db/ticket deps <id>
+tooling/db/ticket dep add <blocker_id> <blocked_id>
+tooling/db/ticket dep rm <blocker_id> <blocked_id>
+
+# WIP
+tooling/db/ticket wip
+
+# Milestones
+tooling/db/ticket milestone list [--status S]
+tooling/db/ticket milestone create <name> [--description TEXT] [--phase N]
+tooling/db/ticket milestone link <ticket_id> <milestone_id>
+tooling/db/ticket milestone unlink <ticket_id> <milestone_id>
+tooling/db/ticket milestone complete <milestone_id>
+tooling/db/ticket milestone show <milestone_id>
+tooling/db/ticket milestone dep <blocker_id> <blocked_id>
 ```
 
 ## Key rules
@@ -37,3 +54,4 @@ tooling/db/ticket assign <id> <agent>
 - **Quote the title** — always wrap in double quotes to handle spaces
 - **Never use `sqlite3` CLI** — it crashes (std::bad_alloc). Use `tooling/db/sqlite-query` or `tooling/db/sqlite-exec` for raw SQL
 - **Verify after create** — run `tooling/db/ticket show <id>` to confirm the title is clean
+- **Milestones are many-to-many** — a ticket can be linked to multiple milestones via `milestone link`