docs: centralise test counts + add release-policy + remove stale stub references

Two complementary improvements aimed at reducing recurring maintenance
overhead:

1. **Test-count centralisation** — `doc/api/tests.md` is now the
   single source of truth for the test counts.  All other docs
   (README, CLAUDE.md, doc/contributing.md, doc/getting-started.md,
   doc/math/validation.md, doc/math/validation-protocol.md,
   scripts/try_it.sh) use qualitative phrasing + a link instead of
   hardcoded numbers.  The previous regime had eight places with
   "227 CGAL tests, 23 non-CGAL tests" that drifted apart across
   releases (the v0.9.0 release-prep needed to touch nine files).

2. **Versioning policy** — `doc/release-policy.md` (new, ~250 lines)
   formalises:
   * SemVer rules for the pre-1.0 and post-1.0 phases.
   * Phase-milestone → MINOR-bump mapping (v0.10.0 → Phase 9c, …).
   * Single-source-of-truth table for moving numbers (test counts,
     version, date).
   * Step-by-step release process (the recipe that worked for v0.9.0
     after the false-start with PR #11/#12).
   * Hotfix policy + post-1.0 deprecation policy.
   * Known failure modes and how to recover from them.

Plus a small CI gate:

3. **scripts/check-test-counts.sh** — verifies the totals in
   doc/api/tests.md match `ctest` output.  Re-uses existing build-cgal/
   if present.  Exit 0 on match, 1 on divergence with recovery hints.
   Cheap enough (~30 s) to run on every PR.

Other cleanups
──────────────
* code/tests/cgal/CMakeLists.txt — stale "Test 7 (genus-2 homology)
  as GTEST_SKIP stub until Phase 8" comment removed; that test landed
  as HomologyGenerators.Genus2_FourCutEdges in Phase 7.
* CLAUDE.md — "test-fast also runs stubs" Known Quirks entry updated
  to reflect the v0.9.0 stub cleanup (no GTEST_SKIPs remain).
* CLAUDE.md doc map — new entry for doc/release-policy.md.

Stubs audit
───────────
Zero GTEST_SKIP() calls remain in the codebase as of this commit.
The only references to stubs are in historical documentation
(CHANGELOG.md v0.7.0 entry, doc/roadmap/* "deferred to research-track"
notes) — those are intended.

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

CLAUDE.md

@@ -244,7 +244,7 @@ Two jobs in `.gitea/workflows/cpp-tests.yml`:
 
 Runner: `eulernest` — self-hosted Raspberry Pi, ARM64, Ubuntu 22.04. Docker image: `git.eulernest.eu/conformallab/ci-cpp:latest`. `test-cgal` needs `test-fast` to pass first (`needs: test-fast`).
 
-Expected results: **23 non-CGAL tests pass**, **227 CGAL tests pass, 0 skipped**.
+Expected results: full test suite passing, 0 skipped, 0 failed.  The canonical counts live in `doc/api/tests.md` — do not hardcode them anywhere else (see [`doc/release-policy.md`](doc/release-policy.md)).
 
 ## Release state
 
@@ -349,7 +349,7 @@ follow the empirical verification rule above before any new claim.
 | Full pipeline API for all three geometries | `doc/api/pipeline.md` |
 | What does each processing unit require/provide (contracts)? | `doc/api/contracts.md` |
 | How to add a new functional / geometry mode / port from Java | `doc/api/extending.md` |
-| All 39 test suites, 227+23 tests, individual counts | `doc/api/tests.md` |
+| Per-suite breakdown and counts (single source of truth) | `doc/api/tests.md` |
 | Phase 8 CGAL package design + Declarative YAML pipeline spec | `doc/api/cgal-package.md` |
 
 ### Concepts & specs
@@ -373,6 +373,7 @@ follow the empirical verification rule above before any new claim.
 | Build modes, single-test invocation, CLI, Docker image rebuild | `doc/getting-started.md` |
 | Step-by-step: port the Inversive Distance functional (Phase 9a template) | `doc/tutorials/add-inversive-distance.md` |
 | Language policy, test standards, release flow | `doc/contributing.md` |
+| Versioning rules + release process + single-source-of-truth list | `doc/release-policy.md` |
 
 ### geometry-central context
 
@@ -386,7 +387,7 @@ Optional adoption roadmap (GC-1/2/3): `doc/roadmap/phases.md` (Optional section)
 
 ## Known quirks
 
-- **`test-fast` also runs stubs**: `conformallab_tests` (non-CGAL) contains `GTEST_SKIP`-based stubs for functionals that need CGAL. This is intentional — those tests document what was in the Java port scope but requires the CGAL mesh type.
+- **No GTEST_SKIP stubs remain** (since v0.9.0): the three stale HDS-port stub files were removed because the CGAL test suite covers the same functionality with real tests.  The pure-math `conformallab_tests` target now only contains active tests.
 - **Boost is header-only**: CGAL 6.x uses only Boost headers (`Boost.Config`, `Boost.Graph`). No compiled Boost libraries are needed. `find_package(Boost REQUIRED)` only locates the include path.
 - **`main` branch is protected** on `origin` (Gitea). Push to `dev`, then merge via pull request. Codeberg `main` can be pushed to directly.
 - **Both remotes must stay in sync**: `origin` = `git.eulernest.eu` (CI runs here), `codeberg` = `codeberg.org/TMoussa/ConformalLabpp` (public mirror). Push to both after every significant change.