Export the canonical 341-repository paired test-fleet index

[ORESoftware]

What changed

• add a deterministic JSON exporter for the full paired test-fleet manifest
• include retained, governance, specialized, managed, and expected repository names and counts per organization
• enforce the exact live totals: 18 pairs, 22 retained, 301 specialized, 18 governance, 319 managed, and 341 expected
• keep r2g and r2g-test explicitly excluded
• add contract tests for global totals, per-org uniqueness, and high-depth product counts
• publish the full canonical index to the GitHub Actions job summary for future audits

Why

A prior exported snapshot had fallen behind the live fleet manifest. This feature makes the current source of truth machine-readable and CI-verified, preventing future repository audits from silently using stale counts or names.

Validation

• node --test tests/test-org-fleet.test.mjs tests/generated-plan-validator-gitlinks.test.mjs tests/export-test-org-fleet-index.test.mjs
• manifest validation
• write-free bootstrap dry run
• read-only workflow permissions and commit-pinned checkout

This PR follows the merged recursive-gitlink fix in #93.

[linear-code]

DEN-2196