Add repository agent development workflows

[SihaoLiu]

Summary

Add repository-owned policy and reusable workflows for coding agents working on Loom. The policy directs product semantics to the existing documentation owners, keeps implementation authority in source, and preserves the boundary between private research planning and public delivery.

Issue

No public Issue was created. The repository owner explicitly authorized direct pull request delivery for this repository-infrastructure change.

Specification And Rationale

• Normative WHAT owner: Repository infrastructure only; Loom product WHAT remains in docs/spec-*.md.
• Rationale WHY owner: Not applicable; existing product rationales remain in docs/rationales/.
• Preceding documentation commit: b218a5cae Define repository agent development policy
• Product semantics unchanged: Yes

Implementation

• Add a root AGENTS.md with architecture orientation, documentation authority, engineering rules, workspace policy, and GitHub privacy boundaries.
• Add repository skills for specification-driven changes, evidence audits, context recovery, worktree delivery, and GitHub research delivery.
• Add a read-only rollout context extractor with normalized fork-prefix validation and fail-closed ambiguity handling.
• Add public bug and implementation-change Issue forms and a pull request template.
• Keep product schemas, architecture contracts, implementation behavior, and private research Projects unchanged.

Evidence

• make doctor
• git fetch https://github.com/PolyArch/loom.git main
• git diff "$(git merge-base HEAD FETCH_HEAD)"...HEAD --check
• ruff check .agents/skills/loom-context-recovery/scripts/extract_rollout_context.py
• ruff format --check .agents/skills/loom-context-recovery/scripts/extract_rollout_context.py
• The skill validator accepted all five skill directories.
• Skill metadata and Issue forms parsed successfully as YAML.
• Relative Markdown links resolved successfully.
• All added files passed ASCII and trailing-whitespace checks.
• Recovery checks covered forked and non-forked local rollouts and rejected a mismatched parent identity.
• Every commit in the pull request was scanned for maintainer-specific home directories, organization-internal storage paths, and site-local EDA library hints; none remain.

No Loom product build or test suite was run because the change is not registered in the product build or runtime paths.

Known Limits

• CI/CD, repository rulesets, and merge automation are not included.
• No private research Project configuration or content is changed.
• Ambiguous rollout forks require an independently verified native boundary.
• The workflows guide repository development but do not define Loom product semantics.

Review Checklist

• The change follows the current documentation authority.
• No private Project roadmap, comment, date, blocker graph, or unpublished evidence is disclosed.
• No credential, restricted artifact, site-local path, or generated commercial-tool output is tracked.
• No unnecessary product test was added.
• The final combined revision was validated at the fidelity required by this repository-infrastructure change.
• Commit messages and this pull request are English-only and contain no automated-tool attribution.