feat(cli): add manus-agent advisory subcommand for GitHub Security Advisory lookup

[manus-use]

Summary

Add manus-agent advisory <CVE-ID> CLI subcommand that fetches GitHub Security Advisory (GHSA) details for a given CVE from the public GitHub Advisory Database.

What this PR does

1. Refactors get_github_advisory.py — extracts a reusable fetch_github_advisory() library function (no Strands dependency) that the CLI and the agent tool both call. The @tool-decorated wrapper now delegates to this function.

2. Adds advisory CLI subcommand — users can look up GHSA data from the terminal without spinning up the full agent:

   manus-agent advisory CVE-2024-3094
   manus-agent advisory CVE-2023-44487 --output json | jq .vulnerabilities

3. Rich text output displays:

   • GHSA ID, severity, published/updated/withdrawn dates
   • CVSS score and vector string
   • CWE classifications
   • Affected packages with vulnerable version ranges and patched versions
   • References (truncated at 10)
   • Credits

4. 33 new tests (tests/test_cli_advisory.py) — 100% mocked, no real HTTP calls. Covers text output, JSON output, edge cases (no CVSS, no CWEs, withdrawn advisories, long descriptions, string references), and the library function directly.

5. README updates — TOC entry + documentation section for the new subcommand.

Test results

1191 passed, 3 deselected, 3 warnings in 25.48s

All existing tests continue to pass. Zero failures.

Duplicate check

Checked all 46 open PRs (#53, #54, #58, #60, #64, #65, #67, #74-90, #96, #98, #100, #103-127) and 30 most recent merged PRs. No existing open or merged PR adds an advisory CLI subcommand. PR #92 (merged) adds tool-level tests for get_github_advisory but does not touch the CLI.