fix(deps): hold pyjwt>=2.14.0 and document mcp 2.2.0 HTTP session limits

[blackaxgit]

Why

After merging #62, #63 and #64, main CI is red. The Dependency audit job fails and Docker Build & Push is skipped, so no image has been published from those merges. The cause is ten advisories published today against pyjwt 2.13.0: CVE-2026-101917, CVE-2026-102265..102269 and CVE-2026-102271..102274, all fixed in 2.14.0. They are not introduced by #64: origin/main had the same pyjwt 2.13.0 lock before the merges, and the last green daily audit ran at 12:14Z.

None of them can be reached from ssh-mcp. In mcp 2.2.0 the only import jwt is mcp/client/auth/extensions/client_credentials.py. That is an OAuth client extension, and ssh_mcp never imports it.

What

• pyproject.toml: adds pyjwt>=2.14.0 under [tool.uv] constraint-dependencies. This is the transitive-floor convention already used for click/cryptography, so the wheel's Requires-Dist does not change. tests/test_dependency_floors.py gets the matching SECURITY_FLOORS entry.
• uv.lock: uv lock --upgrade-package pyjwt. Only pyjwt moves (2.13.0 -> 2.15.1), plus the manifest constraint.
• CHANGELOG.md [Unreleased]: a Security entry for the above, and a Changed entry for the stateful-session limits that mcp 2.2.0 (chore(deps): bump the python-version-updates group across 1 directory with 4 updates #64) introduced: a 30-minute idle expiry and a 10,000-session cap, legacy protocol only; stateless mode avoids both. README.md gets the same information in one sentence.
• Line citations updated to mcp 2.2.0 in AGENTS.md and in comments only in src/ssh_mcp/server.py. The AST is unchanged apart from docstrings. The test count in AGENTS.md is updated to 850.

Verification

• HYPOTHESIS_PROFILE=ci pytest: 850 passed. ruff format/check, mypy, bandit, uv lock --check, pip-audit (no known vulnerabilities), and gitleaks over origin/main..HEAD are all clean.
• Smoke test on a loopback HTTP transport with a throwaway config: initialize, tools/list (6 tools), and a bogus session id returns 404 Session not found, as documented.
• Review panel with no fallbacks: claude-fable-5-1, gpt-6.1-sol and grok-4.7-high in round 1, then fable and sol confirmed the fixes (both PASS).