[AAASM-3939] 📝 (workspace): Add org-level AI workspace layout doc

[Chisanan232]

Jira Ticket

• AAASM-3939

Summary

• Defines the org-level AI workspace layout for the AAASM-3938 onboarding POC: what lives at the workspace root vs. each repo root, and how the .github repo participates as source-of-truth/bootstrap source.

Changes

• Add .claude/WORKSPACE.md documenting: proposed local workspace layout, workspace-root responsibilities, repo-root responsibilities, .github repo's role, the override model (repo-local .claude/rules|skills shadow org-level ones by filename), and explicit Claude Code / Codex discovery assumptions (nearest-directory-wins, no cross-repo auto-fetch).

Validation

• Content reviewed for accuracy
• Links verified
• No unintended scope changes

Checklist

• PR title follows: [<ticket ID>] <GitEmoji> (<change scope category>): <key point as summary>
• PR body follows this template

[Chisanan232]

Claude Code review — AAASM-3939

CI: Red, but root cause is infra, not this change. ci-success.yml runs (event=push) with zero jobs and instant failure — same 0-job/0s pattern also hits the unrelated, already-merged #24 merge commit on master. Check-suites show GitHub Actions: failure while SonarQubeCloud/Codecov/Cloudflare Pages stay stuck queued — consistent with this org's own documented "GitHub Actions frequently billing-blocked" CI reality (see this repo's CLAUDE.md). Not fixable by a code change in this PR; recommend merging on green local validation and treating the Actions billing block as a separate ops item.

Scope vs ticket: Matches all AAASM-3939 acceptance criteria — workspace-root vs repo-root responsibilities, .github's bootstrap/source-of-truth role, override model, and explicit Claude Code/Codex discovery assumptions are all present in .claude/WORKSPACE.md.

Side effects: None — single new file, no existing content touched.

Frontend: N/A, no FE code in this change.

Recommend: ready to merge first in the stack (no dependencies).