fix(api): normalize trailing slashes — no slash on param routes

Rule: trailing slash only on collection roots (/). Any route containing
a path parameter {…} uses no trailing slash. Applies across all routers,
scripts, Makefile, and tests. Fixes 307-redirect fragility on POST/PATCH
from naive clients (curl, Codex HTTP calls).

Also adds POST /repos/{slug}/sync — runs ADR-001 consistency check with
--fix via HTTP, so non-MCP agents (Codex) can self-service DB sync without
operator intervention.

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

api/routers/technical_debt.py

@@ -110,7 +110,7 @@ async def defer_td(
 
 # ── Notes ─────────────────────────────────────────────────────────────────────
 
-@router.get("/{td_id}/notes/", response_model=list[TDNoteRead])
+@router.get("/{td_id}/notes", response_model=list[TDNoteRead])
 async def list_notes(
     td_id: uuid.UUID,
     session: AsyncSession = Depends(get_session),
@@ -124,7 +124,7 @@ async def list_notes(
     return list(result.scalars().all())
 
 
-@router.post("/{td_id}/notes/", response_model=TDNoteRead, status_code=status.HTTP_201_CREATED)
+@router.post("/{td_id}/notes", response_model=TDNoteRead, status_code=status.HTTP_201_CREATED)
 async def add_note(
     td_id: uuid.UUID,
     body: TDNoteCreate,