chore(governance): populate empty .github/CODEOWNERS (#82)

## Summary

`.github/CODEOWNERS` was an empty file. This populates it to mirror the
sibling [echidna repo's
CODEOWNERS](https://github.com/hyperpolymath/echidna/blob/main/.github/CODEOWNERS):

- Default owner `* @hyperpolymath` so PR review notifications route
correctly
- Explicit path entries for `/src/`, `/crates/`, `/.github/`,
`/scripts/`, `/.machine_readable/`

## Out of scope (filed separately)

The dot/config audit also surfaced `.gitignore` + `.gitattributes`
carrying `SPDX-License-Identifier: PMPL-1.0` instead of MPL-2.0 (the
sole-repo default). That is a licence edit and per the owner directive
must be done **manually, file-by-file, owner-only** — filed as a
tracking issue.

## Test plan

- [ ] CODEOWNERS file is non-empty
- [ ] GitHub recognises hyperpolymath as code owner
- [ ] Future PRs auto-request review from @hyperpolymath

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.github/CODEOWNERS

@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: MPL-2.0
+# CODEOWNERS - Code ownership for echidnabot
+# See https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners
+
+# Default owner for everything
+* @hyperpolymath
+
+# Core bot crates
+/src/ @hyperpolymath
+/crates/ @hyperpolymath
+
+# Infrastructure and CI/CD
+/.github/ @hyperpolymath
+/scripts/ @hyperpolymath
+
+# SCM and machine-readable metadata
+/.machine_readable/ @hyperpolymath