chore(llm-security): v7.3.1 — stabilization patch for forkers and downstream users

No behavior changes. Sets the public stance, tightens documentation, and
removes coherence drift so anyone forking or downloading the plugin gets
a consistent starting point.

Added:
- CONTRIBUTING.md — public fork-and-own guide. Why PRs are not accepted,
  how to fork well, what is welcome via issues.
- README "Project scope" section — out-of-scope table naming what is
  fork-and-own territory (web dashboard, fleet policy, runtime firewall,
  IDE LSP, compliance pack, ticketing, multi-tenancy, ML detectors,
  marketplace UI, SSO/SCIM/RBAC) with commercial alternatives.
- package.json: bugs.url, CONTRIBUTING/SECURITY/CHANGELOG in files
  whitelist for npm publishing.

Changed:
- SECURITY.md rewritten. Supported-versions table from stale 5.1.x to
  current reality (7.3.x active, 7.0-7.2 best-effort, <7.0 EOL).
  Best-effort solo response timeline. Scope expanded to bin/.
- Scanner VERSION constants synced to plugin version. Was 6.0.0 in
  dashboard-aggregator and posture-scanner.
- package.json repository.url corrected from fromaitochitta/ to open/.
- README "Feedback & contributing" links to CONTRIBUTING.md.

Fixed:
- pre-compact-scan size-cap timing test ceiling raised 500ms -> 1000ms.
  Was a flake on Intel Mac and CI under load. Design target unchanged
  (<500ms, documented in CLAUDE.md).

Notes:
- First patch on the stabilization line (post-2026-05-01).
- Wave E attack-simulator scenarios deferred indefinitely; coverage
  remains at 72.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

plugins/llm-security/CHANGELOG.md

@@ -4,6 +4,72 @@ All notable changes to the LLM Security Plugin are documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
+## [7.3.1] - 2026-05-01
+
+Stabilization patch. No behavior changes. Sets the public stance, tightens
+documentation, and removes coherence drift so forkers and downstream
+organizations get a consistent starting point.
+
+### Added
+
+- `CONTRIBUTING.md` — public fork-and-own guide. Explains why PRs are not
+  accepted on the upstream repo, how to fork well (rename plugin, change
+  security contact, preserve LICENSE, re-establish trust), what is welcome
+  via issues, and the bar for inline-diff suggestions the maintainer may
+  apply directly.
+- `README.md` "Project scope" section — public statement of stabilization
+  mode (effective 2026-05-01) plus an out-of-scope table naming what is
+  fork-and-own territory: web dashboard, fleet policy server, runtime
+  prompt firewall, IDE LSP, compliance PDF/DOCX pack, enterprise ticketing
+  connectors, multi-tenancy, ML-based detectors, marketplace UI,
+  SSO/SCIM/RBAC. Each row points at the commercial alternative
+  (Snyk, Lakera, Vanta, Splunk SOAR, parry-guard, etc.).
+- `package.json`: `bugs.url` field, `CONTRIBUTING.md` / `SECURITY.md` /
+  `CHANGELOG.md` added to the `files` whitelist so npm-published artifacts
+  ship with full project documentation.
+
+### Changed
+
+- `SECURITY.md` rewritten. Supported-versions table moves from `5.1.x`
+  (stale since v6.0.0) to current reality: 7.3.x active, 7.0–7.2 best-effort,
+  < 7.0 EOL. Adds explicit best-effort solo-project response timeline (7
+  days ack, 14 days triage, 30 days fix for High/Critical), expands scope
+  list to cover `bin/llm-security.mjs`, and notes that out-of-scope
+  vulnerabilities (e.g., adaptive ML-based bypass) get an explanatory
+  response rather than silent ignore.
+- `README.md` "Feedback & contributing" section now links to
+  `CONTRIBUTING.md` and the new "Project scope" section.
+- `package.json` `repository.url` corrected from
+  `fromaitochitta/claude-code-llm-security` to
+  `open/claude-code-llm-security` (matches `homepage` and the canonical
+  Forgejo path).
+- Scanner `VERSION` constants synced to plugin version. Previously
+  `dashboard-aggregator.mjs` and `posture-scanner.mjs` reported `6.0.0`
+  in scan output and SARIF, mismatching the actual plugin version.
+  All three standalone scanners (`dashboard-aggregator`, `posture-scanner`,
+  `ide-extension-scanner`) now report `7.3.1`.
+
+### Fixed
+
+- `tests/hooks/pre-compact-scan.test.mjs` size-cap timing test ceiling
+  raised from 500 ms to 1000 ms. The 500 ms hard cap was a flake source
+  on Intel Mac and CI runners under load, while the design target
+  (documented in `CLAUDE.md`) remains <500 ms. The test now catches
+  order-of-magnitude regressions without breaking on hardware/CI noise.
+
+### Notes
+
+- This is the first patch on the stabilization line. Future 7.3.x
+  releases will be limited to bug + security fixes and small
+  knowledge-base refreshes that fit the existing deterministic
+  architecture. v8.0.0 remains scheduled as the deprecation cleanup
+  for the env vars and `riskScoreV1` constant deprecated in v7.3.0;
+  see "Project scope" in `README.md` for the longer-term direction.
+- Wave E (additional attack-simulator scenarios mentioned in the v7.3.0
+  changelog as "deferred to v7.3.1") is now deferred indefinitely.
+  Coverage remains at 72 scenarios. Forkers who want broader red-team
+  coverage are encouraged to extend `knowledge/attack-scenarios.json`.
+
 ## [7.3.0] - 2026-05-01
 
 Batch C release. Closes 12 implementation tasks (E3, E8-E14, 8.4, 8.6,