feat(conventions): generalize defaults, backfill old projects, adopt the standard in-repo

Harden the architectural-conventions standard so it works out-of-the-box on
any project and resolves for projects that predate it, and make RoboCo pass
its own gate.

General defaults (apply to every project, not just one with a tuned file):
- The auto-scan excludes test and documentation trees (tests/, docs/) — those
  legitimately define fixtures and aren't enforced code.
- Helper placement seeds at warn, not block: `helper` matches any top-level
  function, too blunt a signal to hard-block a route file's small private glue.
  Misplaced model/route/component stay block; the body-level thin_routes check
  remains the real fat-handler guard.
- thin_routes no longer counts transaction-lifecycle calls (commit/flush/
  refresh) as data access — an explicit `db.commit()` after delegating to a
  service is a valid pattern.
- no_lint_suppressions exempts a small allowlist of structurally-unavoidable
  framework codes (ruff TC001-TC003, pydantic prop-decorator); bare or other
  suppressions still flag.
- CLAUDE.md rule-lifting skips bare common-word tokens that would match
  everywhere (e.g. "commit"), keeping only specific identifiers.
- The ambient prompt block lists only constrained modules and truncates at a
  line boundary with a "+N more" pointer instead of cutting mid-line.

Backfill: the standard previously read the committed file + repo scan from
project.workspace_path, a field only a manual API call set — so an older
project (or one whose workspace was cleared) showed an empty "missing" map no
matter what was pushed. The service now ensures a dedicated, default-branch
read clone on demand (WorkspaceService.ensure_read_clone) and resolves from
it, persisting the resolved path + real HEAD. The panel tab, the spawn-time
ambient block, and the per-task constraints all resolve the committed standard
with no manual setup.

Adopt in-repo: relocate the inline request/response models from the system and
*_live route modules into roboco/api/schemas/ so the codebase passes its own
placement gate, and ship a canonical .roboco/conventions.yml. no_models_in_routes
and modular_cohesion are now clean and enforced at block.

Docs updated across the user guide, the agent-facing RAG standard, the
developer and pr_reviewer role prompts, CLAUDE.md, and the changelog. New unit
tests cover the scan exclusions, helper-warn, the suppression allowlist, the
commit exemption, and the resolve/backfill path; the conventions + project
integration suites pass against Postgres.

CLAUDE.md

@@ -377,9 +377,9 @@ Agent backends are pluggable. `roboco/llm/providers/` defines an `AgentProvider`
 
 ## Architectural Conventions Standard
 
-**Per-project architectural standard (default-off).** Beyond the `make`-style gates (which check syntax/types/tests, not *where code lives*), each project can carry a repo-canonical `.roboco/conventions.yml` — an architecture map (which definition *kinds* belong in which modules), a toggleable rule set, custom regex rules, and waivers — so an agent cannot land a Pydantic model defined inside a router, a helper in a route file, or a `# noqa` / `# type: ignore`. Gated by `ROBOCO_CONVENTIONS_ENABLED`; fully inert when off.
+**Per-project architectural standard (default-off).** Beyond the `make`-style gates (which check syntax/types/tests, not *where code lives*), each project can carry a repo-canonical `.roboco/conventions.yml` — an architecture map (which definition *kinds* belong in which modules), a toggleable rule set, custom regex rules, and waivers — so an agent cannot land a Pydantic model defined inside a router or a `# noqa` / `# type: ignore`. Placement of a *helper* (any top-level function) only **warns** — too blunt to hard-block; `thin_routes` doesn't count an explicit `db.commit()`; and a small allowlist of unavoidable framework suppressions (ruff `TC001`–`TC003`, pydantic `prop-decorator`) is exempt. Gated by `ROBOCO_CONVENTIONS_ENABLED`; fully inert when off. RoboCo itself ships a canonical `.roboco/conventions.yml`.
 
-**Effective map.** Consumers read the *effective* map — auto-derived defaults (from a repo scan + `BUILTIN_RULES`) overlaid by the committed file — so behaviour is identical whether the file is present, absent, or partial. `ConventionsService` (`roboco/services/conventions.py`) builds it, caches it per `(project, HEAD sha)` in `project_conventions_cache` (migration `043`), renders the per-task baseline constraints + the ambient prompt block, and scaffolds/restores the file via a PR (`GitService.open_conventions_pr`). The schema lives in `roboco/foundation/policy/conventions/` (pure).
+**Effective map.** Consumers read the *effective* map — auto-derived defaults (from a repo scan + `BUILTIN_RULES`, excluding `tests/`/`docs/` trees) overlaid by the committed file — so behaviour is identical whether the file is present, absent, or partial. `ConventionsService` (`roboco/services/conventions.py`) builds it, caches it per `(project, HEAD sha)` in `project_conventions_cache` (migration `043`), renders the per-task baseline constraints + the ambient prompt block, and scaffolds/restores the file via a PR (`GitService.open_conventions_pr`). The committed file + scan are read from a dedicated project-level **read clone** the service ensures on demand (`WorkspaceService.ensure_read_clone`, pinned to the default branch's HEAD) — the backfill that makes the standard resolve even for a project created before it existed, with no manual `workspace_path`. The schema lives in `roboco/foundation/policy/conventions/` (pure).
 
 **Validator.** A single Python CLI, `python -m roboco.conventions check --root <repo> --files <a> <b> ...` (`roboco/conventions/`), uses tree-sitter (Python + TypeScript grammars, shipped in the agent image) to classify each changed definition and flag forbidden placements + hygiene + custom-rule matches as JSONL findings, after waiver filtering. Precision over recall (it abstains when uncertain so a `block` gate can't false-positive-strand a task) and fail-loud (a validator that cannot run exits 3 so the gate blocks, never silently passes).