docs: clarify agent workflow and branch naming rules

[hetaoBackend]

Change

Clarify AGENTS.md so new branches use purpose-based names such as feat/*, fix/*, and docs/*, with lowercase kebab-case descriptions. Explicitly exclude agent/tool prefixes such as codex/, while respecting a branch name explicitly requested by the user.

Correct the distinction between Vitest and Node test registration, document source-export prerequisites and verification profile selection, and clarify inventory regeneration and public-source review boundaries. Only AGENTS.md changes.

Validation

• pnpm verify: all 14 gates passed on macOS arm64, Node.js 26.4.0, full profile, revision 596856e1a660e0a72fce48780311ca85e82b0b7f.
• git diff --check: passed.
• Confirmed AGENTS.md changes select full CI under the existing change classifier.
• NOT RUN locally: Linux/Windows validation and live-model/service acceptance. Offline tests are not live-service acceptance.

Publication and contribution checks

• I have permission to contribute these changes under the existing licenses applicable to the changed files/packages; imported material and its provenance are identified and existing notices are preserved.
• No credentials, account data, real user content, internal source history or private review material is included.
• Added/removed source files were reviewed before regenerating release/public-source.json; new tests are declared in test/vitest-suites.json where applicable. No files or tests were added or removed; no regeneration was needed.
• Shared English/Chinese documentation and capability/verification records are updated where applicable. Mock/offline results are not described as live-service acceptance. README and product behavior are unchanged.

Maintainer handoff

Publication scope or license changes: none.

Shared-source port: not needed; this updates public-repository agent guidance only.

---

^{Need help on this PR? Tag @codesmith-bot with what you need. Autofix is disabled.}