docs(governance): add repository contribution controls

[srpatcha]

Fixes #30

Summary

• replace the generic agent scaffold with eBrowser-specific C11 architecture, portability, security-boundary, and target-validation guidance
• add the canonical linked-issue workflow pinned to 92cb596c773496ec4df76717e8acf0e6b7700f73
• require a recognized same-repository closing issue while preserving the local change-type, testing, screenshots/logs, and notes sections
• snapshot all six published Wiki pages under docs/wiki/ from Wiki revision a4ab6d9164e3802b09d73bdc98b9cf83bd8325b7

Validation

• YAML parsed successfully and the workflow matches the canonical template after exact SHA substitution
• npx --yes markdownlint-cli2 AGENTS.md .github/PULL_REQUEST_TEMPLATE.md: 0 errors
• all six relative Wiki link targets resolve and the files match the published Wiki byte-for-byte
• python -m pytest tests/unit tests/functional tests/performance tests/simulation -v: 26 passed
• git diff --check: passed

Risk and rollout

Documentation and pull-request policy only. The reusable workflow has read-only permissions. On Windows, the repository's tracked include/eBrowser -> ebrowser symlink cannot materialize beside include/ebrowser; that checkout-only deletion is not included in this commit.

[srpatcha]

CI audit for run 34547841364 (head e9e3d3d):

• The failures are not caused by this contribution. PR docs(governance): add repository contribution controls #31 does not change .github/workflows/ci.yml, Python sources, requirements.txt, or pyproject.toml.
• All six Ubuntu/Windows matrix jobs installed Python, then failed inside actions/setup-python@v5 cache setup because no requirements.txt or pyproject.toml exists. The three macos-13 jobs never acquired a runner and were cancelled after 24 hours.
• Current master at bb37c5b fails the same workflow in run 33500801186 with the same six setup-python failures and three macOS cancellations: https://github.com/embeddedos-org/eBrowser/actions/runs/33500801186
• Local PR-head validation: all 26 Python tests passed; the documented Markdown lint for AGENTS.md and .github/PULL_REQUEST_TEMPLATE.md reported 0 errors; both workflow YAML files parse; git diff --check origin/master...HEAD passed.
• Repository-wide Ruff reports the same 103 pre-existing promo/promo_scene.py errors on PR head and master. Native CMake configuration succeeds, but the Windows build hits the pre-existing tests/benchmark.c dependency on unistd.h.

No PR changes were made: fixing the baseline CI/package contract or macOS runner availability would be unrelated scope. Failed run: https://github.com/embeddedos-org/eBrowser/actions/runs/34547841364