[5/7] --pick-team / re-pick across all hierarchy levels

[shouze]

Context

applyTeamPick, moveRepoToSection, undoSectionPick, undoPickedRepo in src/group.ts address sections by their flat label string. Once sections form a tree, a label alone is no longer unique (e.g. "other" can appear under multiple parent branches), so --pick-team and the interactive p/t pick/re-pick flows need a new addressing scheme.

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

Solution

• Introduce a path-based section identifier (e.g. "gamme-lead-client > squad-dashboard") used internally to disambiguate sections, while keeping the CLI syntax as ergonomic as possible (resolve by nearest-unique-label match, falling back to full path only when ambiguous).
• Update applyTeamPick, moveRepoToSection, undoSectionPick, undoPickedRepo to operate on the tree/path model from [1/7] Data model & core hierarchical grouping algorithm #177.
• Update replay command emission ([3/7] Markdown & JSON output for N-level headings #179's ReplayOptions) and stderr validation/warning messages for ambiguous or not-found labels.
• Update the TUI so p (pick) and t (re-pick) work when the cursor rests on a combined section header at any depth ([4/7] TUI rendering & navigation for N-level headers #180's row model).

Acceptance Criteria

• --pick-team "<combined>=<chosen>" resolves correctly when the combined label is unique across the tree.
• When a combined label is ambiguous (appears under multiple parents), a clear stderr warning lists the candidates / expected path syntax.
• Interactive pick (p) and re-pick (t) work on any header depth in the TUI.
• The replay command reproduces multi-level picks exactly.

Definition of Done

• Full test coverage in src/group.test.ts for path addressing and ambiguity resolution.
• docs/usage/team-grouping.md pick-team section flagged for update in issue v1.0.4 #7 (not required in this PR).
• bun test, bun run lint, bun run format:check, bun run knip, bun run build.ts all green.
• Depends on [1/7] Data model & core hierarchical grouping algorithm #177, [3/7] Markdown & JSON output for N-level headings #179, [4/7] TUI rendering & navigation for N-level headers #180 being merged first.