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/agents/README.md

@@ -34,7 +34,8 @@ All agents read their briefing file at `docs/briefings/{name}.md` before startin
 
 | Agent | File | Role | Model | When to use |
 |-------|------|------|-------|-------------|
-| `si` | si.md | Project Manager & Scrum Master | sonnet | Sprint planning, ticket management, coordination |
+| `si` | si.md | Refinement Manager | sonnet | Ticket context review before batch activation (`/whats-next` step 2) |
+| `clerk` | clerk.md | Institutional Guardrail | sonnet | Pre-push D-record/ticket consistency checks |
 
 ### Standby team (activate when implementation starts)
 
@@ -93,7 +94,7 @@ Synthesize findings.
 | Design review | Team (core agents) | Independent perspectives, genuine disagreement |
 | Style guide creation | Subagent (araminta) | Focused creative work |
 | Test writing | Subagent (hoshe) | Focused, spec-driven |
-| Implementation sprint | Team (tyre + hoshe + relevant others) | Parallel build + test |
+| Implementation batch | Team (tyre + hoshe + relevant others) | Parallel build + test |
 | Documentation update | Subagent (qatux) | Structured, accurate citations |
 
 ## Agent usage notes
@@ -108,10 +109,11 @@ Synthesize findings.
 - Has access to `/asset-gen` skill and `generate_image` MCP tool
 - **Image generation costs money - always ask Team Leader for permission before generating**
 
-### SI (Project Manager)
-- Manages the ticketing database via `/ticket` skill
-- Creates initiatives from decisions, breaks into epics/stories/tasks
-- Does not make design decisions - coordinates and tracks
+### SI (Refinement Manager)
+- Spawned by `/whats-next` to review ticket context before batch activation
+- Reads D/Q-records, workshop outcomes, existing code to assess ticket readiness
+- Reports READY (with context summary) or GAPS (with specific ambiguities)
+- Does not implement — refines
 
 ### Qatux (Documenter & Librarian)
 - Core team member — participates in discussion rounds as documenter