feat(cli): add --markdown flag to swamp report get

[stack72]

Summary

Closes swamp-club#346.

• Add --markdown flag to swamp report get that emits clean markdown (pipe tables, ## headings, no ANSI escapes or box-drawing) instead of terminal-formatted output
• Mutually exclusive with --json via Cliffy's conflicts declaration
• Uses the existing renderMarkdownPlain() function which was previously unused
• Update swamp-report skill to document the new flag

Test Plan

• 4 new unit tests for the markdown renderer (no ANSI escapes, varySuffix handling, workflow source)
• All 9 renderer tests pass
• deno check / deno lint / deno fmt pass
• Compiled binary and verified --markdown produces clean markdown with real report data
• Verified --markdown --json correctly errors with conflict message

🤖 Generated with Claude Code

[github-actions]

CLI UX Review

Blocking

None.

Suggestions

1. Metadata line formatting (report_get.ts:84): The metadata line in markdown mode — ${source} | Scope: ${r.reportScope} | v${r.version} | ${r.createdAt} — is unstyled prose after a ## heading. On GitHub/Linear it may look a bit unpolished. A > blockquote prefix or _italic_ wrap would give it a distinct metadata treatment. Entirely optional given the stated use-case is piping to a file.

2. ISO timestamp in markdown output (report_get.ts:84): createdAt emits a raw ISO string (2026-01-15T10:00:00.000Z). Fine for scripts, slightly noisy in human-read docs. No action needed.

Verdict

PASS — --markdown is well-named, properly conflicts with --json, has a clear example (> report.md), produces verified ANSI-free output, and follows the same renderer pattern as log/json modes. Skill documentation is clear and complete.

[github-actions]

Code Review

Clean, well-structured PR that adds a --markdown output mode to swamp report get.

Blocking Issues

None.

Suggestions

None — the implementation follows existing patterns closely:

• Import boundary: CLI command imports from libswamp/mod.ts ✓
• Renderer pattern: MarkdownReportGetRenderer follows the same class + factory switch pattern as LogReportGetRenderer and JsonReportGetRenderer ✓
• Type safety: ReportOutputMode = OutputMode | "markdown" cleanly extends the existing type, and the switch in createReportGetRenderer remains exhaustive ✓
• Mutual exclusion: conflicts: ["json"] follows the same Cliffy pattern used elsewhere (e.g., extension_list.ts, issue_ripple.ts) ✓
• Tests: 4 new tests cover the key behaviors (no ANSI escapes, varySuffix presence/absence, workflow source) ✓
• Skill docs: Quick reference table and markdown mode paragraph added in the right places ✓
• Copyright headers: All files have AGPLv3 header ✓
• No security concerns: Boolean flag, no user input flows into dangerous paths ✓