docs: complete project documentation and Gitea CI setup

Add STATUS.md (what's done, verification, future work), GITEA.md (act_runner,
master branch policy, pipeline), and CONTRIBUTING.md (dev guide, new language
checklist). Update README for all 28 validators, docs index, and project tree.

Align Gitea Actions with master as default branch; add PR and issue templates.
Expand .gitignore for debug artifacts and test binaries.

.gitignore

@@ -18,22 +18,17 @@ nimblecache/
 # -- Binaries (compiled output) -------------------------------------------
 bin/
 
-# -- Test compiled binaries (source is .nim, binaries have no extension) --
-tests/test_all
-tests/test_bash
-tests/test_nim
-tests/test_php
-tests/test_python
-tests/test_javascript
-tests/test_js
-tests/test_html
-tests/test_jinja
-tests/test_json
-tests/test_yaml
-tests/test_toml
-tests/test_mixed
-tests/test_config
-tests/test_fuzz
+# -- Test compiled binaries (nim c -r leaves executables without .nim ext) --
+tests/test_*
+!tests/test_*.nim
+
+# -- Local debug / hang investigation (never commit) --
+debug_*
+debug_*.nim
+test_hang*
+tests/mk_debug
+build.tmp
+nimcheck.out
 
 # -- Logs -----------------------------------------------------------------
 *.log