[6/7] CLI wiring end-to-end

[shouze]

Context

github-code-search.ts currently parses --group-by-team-prefix as a flat comma-separated prefix list and calls fetchRepoTeams (src/api.ts) with that flat list; fetchRepoTeams's signature is prefix-list agnostic and does not need to change. This issue integrates all previous sub-issues into the actual CLI surface.

Part of EPIC #125. Depends on #177, #178, #179, #180, #181.

Solution

• Parse the new --group-by-team-prefix chain grammar: / separates hierarchy levels within one chain, , separates independent sibling hierarchies (confirm and document the exact grammar, including edge cases like leading/trailing /, empty segments, duplicate prefixes across chains).
• Flatten all distinct prefix segments across all chains/levels before calling fetchRepoTeams (no changes needed to fetchRepoTeams itself).
• Wire the consolidation flag from [2/7] Advanced consolidated rendering #178 and the pick-team addressing from [5/7] --pick-team / re-pick across all hierarchy levels #181 into the CLI options and validation/warning logic.
• Expand stderr validation messages for malformed chains.

Acceptance Criteria

• --group-by-team-prefix "gamme-/squad-,chapter-" is parsed into one 2-level chain (gamme-, squad-) and one 1-level chain (chapter-).
• Malformed input (empty segment, stray /) produces a clear stderr warning and a sane fallback (e.g. treat as a flat single-level prefix), not a crash.
• End-to-end manual run against a real or fixture GitHub org produces the expected nested markdown/JSON/TUI output.

Definition of Done

• bun test, bun run lint, bun run format:check, bun run knip, bun run build.ts all green.
• Manual end-to-end verification steps documented in the PR.
• Depends on [1/7] Data model & core hierarchical grouping algorithm #177, [2/7] Advanced consolidated rendering #178, [3/7] Markdown & JSON output for N-level headings #179, [4/7] TUI rendering & navigation for N-level headers #180, [5/7] --pick-team / re-pick across all hierarchy levels #181 being merged first.