DEVX-155: Replace pr_review with spec-driven CI gates and pr-review skill

AGENTS.md

@@ -83,7 +83,6 @@ src/devx/
 │   ├── classify_changes.py  # User-facing vs infrastructure change detection
 │   ├── detect_release_commit.py  # Detect release commits on master
 │   ├── validate_commit_msg.py    # Conventional commit validation
-│   ├── pr_review.py     # Automated PR review + manual reviews (--event, --body, --checklist-confirmed)
 │   ├── post_merge.py    # Vikunja task updates after merge
 │   ├── sync_wiki.py     # Sync documentation to Gitea wiki
 │   ├── push_badges.py   # Generate and push quality badges (--retries for retry on git push failures)
@@ -158,8 +157,37 @@ src/devx/
 - **PYTHONPATH: src** — Workflows set `PYTHONPATH: src` (NOT `.:src` since there are no scripts at repo root)
 - **Config via env vars** — `DEVX_*` environment variables with `.env` file fallback
 
+
+## Spec-Driven Development
+
+Every change starts with a spec. No spec, no code.
+
+**Workflow:**
+1. Create Vikunja task → get `<PREFIX>-N` task ID
+2. Write spec at `docs/specs/<TASK-ID>.md` (see template in `.devin/skills/spec-driven-development/SKILL.md`)
+3. Create branch, implement with `# Implements: REQ-N` comments
+4. Tick all acceptance criteria checkboxes in spec
+5. Push and create PR — CI validates spec before expensive jobs
+
+**CI gates (pre-merge):**
+- `devx.ci.validate_spec` — checks spec exists, has required sections, REQ-IDs, all ACs checked
+- `devx.ci.check_pr_size` — max 500 lines / 10 files (excludes CHANGELOG, badges, locks)
+- `devx.ci.fast_molecule` — converge+verify only for changed roles, single platform
+
+**Nightly (infra only):**
+- Full molecule suite (all scenarios, all platforms) + staging deploy + integration tests
+- On failure: sets `NIGHTLY_STATUS=failed`, blocks staging deploys
+- Post-merge auto-deploy to staging checks this gate before deploying
+
+**Post-merge:**
+- Infra: auto-deploys to staging (if nightly gate is green)
+- GRM/sso-bridge: auto-publishes package, auto-creates infra dependency PR to bump pinned version
+
+**Skill:** `.devin/skills/spec-driven-development/SKILL.md` — full template and workflow details.
+
 ## PR Workflow (Mandatory)
 
+
 Every change to master goes through this workflow. No exceptions.
 
 ### Branch Protection (Required Gitea Settings)
@@ -210,7 +238,7 @@ docs: update README
 ### 6. Review the PR
 
 **Automated review (CI `validate` job):** Every PR triggers an automated
-review via `python -m devx.ci.pr_review` as a step in the `validate` job.
+review via the `pr-review` skill (agent-invoked, not a CI step).
 This posts a review with
 `COMMENT` (no issues) or `REQUEST_CHANGES` (issues found):