chore(policy): adopt organization instruction routing

[ss-o]

Summary

Deliver the generated organization routing block in AGENTS.md and add the immutable reusable Org Routing workflow on main. The caller uses organization revision 1becebb7b98dab717d82897428afafd792d4fb97; declared vendored skills match the approved inventory at that revision. Repository-specific instructions are preserved.

Refs z-shell/.github#665. This pull request covers this repository's initial delivery; the wider rollout and enforcement remain open.

Verification

• Published organization scripts/org-routing.py check passed against a clean source snapshot for z-shell/zi-setup.
• Workflow actionlint and Git diff hygiene passed.
• Trunk is not configured in this repository.
• go test ./... and go vet ./... passed in a clean source snapshot.
• Hosted checks and runtime instruction/skill discovery remain unverified at opening.

Agent handoff

Ready for hosted validation and review of record. After landing and observing a successful caller, verify the exact hosted check name before requiring it in branch rules. Delivery does not by itself prove runtime selection or semantic compliance.

[ss-o]

Post-merge review of head fdbca0c8dc894d08c7988d60de354b19a1145dfa.

No findings.

Checked after merge: scripts/org-routing.py check from z-shell/.github main (15d8e2e1) on an export of this head reports routing current (generated block byte-identical, declared surfaces present, no undeclared carriers, vendored skill digests match lib/approved-skills.json). .github/workflows/org-routing.yml is byte-identical to the merged zi#570, F-Sy-H#193 and z-a-eval#12 callers (full-SHA pin, contents: read, no caller concurrency since the reusable workflow sets its own). No added line carries U+2014 or attribution text.