Open Pstack 1.17.3

Adopts Cursor's latest Pstack content at 99743e9c151c8537cbbf1f98bb38f34ef3368453, still version 0.15.25. The catch-up policy maps this same-version update to distribution patch 1.17.3.

• Removes repeated instructions from the migration and type-system principles.
• Removes Interrogate's suggestion to limit actionable findings to five. Real defects remain actionable regardless of count.
• Shortens Swarm while retaining declared coverage, completion, and saved provider recovery rules.

Portable metadata, shared Codex and Claude skills, model descriptors, efforts, spending policy, parent Git ownership, and provider runtime behavior are preserved. These are guidance changes, not new worker capabilities.

PR #149 records validation and review. Normal-budget Linux CI passed 993 tests with five platform skips and none failing. Strict typecheck, static invariants, documentation, maintenance, hook and provenance checks passed. Both real hosts loaded the candidate and exercised supplied controls. All 238 final packaged files match in the dedicated installations. Independent Opus 5.5 source review and native shipping verification both returned PASS+NOTES for the exact final head. The PR records their caveats.

The host controls distinguish six demonstrated defects from preferences, preserve external API compatibility, reject a wrong semantic ID, and report incomplete synthetic coverage. They do not prove a full live Swarm, independent review panel, real provider recovery, automatic skill selection, runtime ID construction, or a completed migration. NOTICE-only provenance changes retain host proof through exact unchanged-file hashes. They do not claim a fresh final-head installer transaction.

Both local full-suite attempts failed. One used a broken default Node 25 binary. The Node 24 run still failed in unchanged timing-sensitive fixtures. Issue #141 tracks that separate work. No runtime, test source, or budgets changed to hide the failures.

Source decisions and exclusions are in release-pinned UPSTREAM.md. The previous immutable release, v1.17.2, is the rollback checkpoint.