feat(tui): add label and milestone filter pane to issues browser

[snipcodeit]

Summary

• Adds lib/tui/filter.cjs — a pure FilterState class that extracts available labels and milestones from the loaded issue set, manages active selections with keyboard-navigable cursor, applies filters client-side before fuzzy search runs, and persists last-used selections to .mgw/config.json
• Adds an interactive filter pane overlay to renderer.cjs that replaces the detail pane when focused — shows label/milestone checkboxes ([x]) and state radio buttons with > cursor highlighting, plus a filter bar summary row showing active filters
• Wires the full filter-then-search pipeline in index.cjs: filterState.apply(issues) narrows the list before FuzzySearch runs, so search works within the filtered view; filter selections persist on pane close
• Adds [f] filter-focus, [Space] filter-toggle, [c] filter-clear, and Ctrl+C force-quit bindings to keyboard.cjs

Closes #119

Milestone Context

• Milestone: v4 — Interactive CLI & TUI
• Phase: 27 — TUI Issue Browser with Fuzzy Search
• Issue: 3 of 9 in milestone

Changes

lib/tui/filter.cjs (new)

• FilterState class: availableLabels, availableMilestones extracted from issue set at construction
• Cursor navigation: cursorDown(), cursorUp(), nextSection(), prevSection() move through Labels/Milestones/State sections
• toggleCursor() — toggles label/milestone membership, selects state option
• apply(issues) — filters by active labels (AND), active milestones (OR), and state; runs before fuzzy search
• clearAll() — resets all selections
• toJSON() / constructor hydration — persistence contract for .mgw/config.json
• extractLabels() and extractMilestones() — exported helpers

lib/tui/renderer.cjs

• Added filterPane (blessed box, overlays detail pane when focusPane === 'filter'): renders label checkboxes, milestone checkboxes, state radio buttons with cursor indicators
• _formatFilterPane(filterState) — builds pane content from FilterState
• _formatFilterBar(filterState) — builds summary row (e.g. Filter: Labels: bug | Milestone: v4)
• Updated render() to show/hide filter pane vs detail pane based on focusPane; passes filterState through
• startKeyboard() updated: in filter mode, j/k/↑/↓ emit filter-scroll-*; Tab/Shift+Tab emit filter-next/prev-section
• Header updated to include [f] filter hint
• Help overlay updated with filter shortcuts

lib/tui/index.cjs

• Imports FilterState from ./filter.cjs
• _loadPersistedFilters() / _savePersistedFilters() — read/write .mgw/config.json tuiFilters key
• CLI initialFilter flags seed the FilterState (label, milestone, state)
• refilter() — recalculates filtered = searchIn(filterState.apply(issues), query) after any filter or search change
• Keyboard handlers: filter-focus, filter-scroll-down/up, filter-next/prev-section, filter-toggle, filter-clear
• help, jump-top/bottom, page-up/down, tab-focus-reverse, force-quit handlers added

lib/tui/keyboard.cjs

• Added 'f': 'filter-focus', ' ': 'filter-toggle', 'c': 'filter-clear', '\u0003': 'force-quit'

Test Plan

• MGW_NO_TUI=1 node -e "require('./lib/tui/filter.cjs')" — module loads without error
• Unit: FilterState label toggle — fs.toggleCursor() on label bug → fs.activeLabels has bug; toggle again → removed
• Unit: FilterState state filter — fs.activeState = 'closed' then fs.apply(issues) returns only closed issues
• Unit: FilterState milestone filter — select milestone v4 → only issues with that milestone returned
• Unit: Filter+search pipeline — filter to milestone v4, then search 'auth' → intersection
• Unit: fs.clearAll() → isEmpty === true
• Unit: fs.toJSON() / constructor hydration round-trip — active selections survive JSON serialisation
• MGW_NO_TUI=1 node bin/mgw.cjs issues --limit 5 — static table renders (no filter pane, no error)
• Interactive TTY: f opens filter pane (detail pane replaced by filter pane with label/milestone/state sections)
• Interactive TTY: j/k navigate cursor within filter pane rows
• Interactive TTY: Tab advances cursor to next section (Labels → Milestones → State → Labels)
• Interactive TTY: Space toggles selected label/milestone; issue list updates in real time
• Interactive TTY: Space on State section selects that state option; list updates
• Interactive TTY: f again closes filter pane (returns to detail pane)
• Interactive TTY: c clears all active filters from anywhere; list returns to full set
• Interactive TTY: filter bar row reflects active filters when filter pane is closed
• Interactive TTY: quit and relaunch — last-used filters restored from .mgw/config.json
• Interactive TTY: Ctrl+C force-quits from filter mode

🤖 Generated with Claude Code

[snipcodeit]

Review: PR #163 — label and milestone filter pane

The FilterState class is well-designed — clean separation of concerns, good persistence contract, and the filter logic (AND for labels, OR for milestones) is correct. However there is one critical runtime bug and several gaps.

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CRITICAL: FuzzySearch.searchIn does not exist

In lib/tui/index.cjs, _applyFiltersAndSearch() calls:

return query ? search.searchIn(afterFilter, query) : afterFilter;

But FuzzySearch (in lib/tui/search.cjs) only exposes a search(query) method that searches this.items — it has no searchIn(subset, query) method. This will throw:

TypeError: search.searchIn is not a function

at runtime the moment a filter is active and the user types a search query. The PR body even acknowledges this: "FuzzySearch does not have a searchIn method — we need a helper that creates a temporary FuzzySearch over a subset." — but no helper was implemented.

Fix options:

1. Add a searchIn(items, query) method to FuzzySearch:

   searchIn(items, query) {
     const temp = new FuzzySearch(items, { keys: this.keys });
     return temp.search(query);
   }

2. Or construct a new FuzzySearch inline in _applyFiltersAndSearch:

   function _applyFiltersAndSearch() {
     const afterFilter = filterState.apply(issues);
     if (!query) return afterFilter;
     const scoped = new FuzzySearch(afterFilter, { keys: ['title', 'number', 'labels'] });
     return scoped.search(query);
   }

Option 1 is cleaner and keeps search.cjs as the single source of search logic.

---

CRITICAL: No test file added for filter.cjs

FilterState is a pure in-memory class with no I/O dependencies — it is ideal for unit testing. The PR test plan lists 17 testable assertions but none are implemented. test/tui-filter.test.cjs should cover:

• extractLabels / extractMilestones deduplication and sort
• Label toggle (add/remove)
• Milestone toggle
• State filter selection via toggleCursor()
• apply() — AND logic for labels, OR logic for milestones, state filtering
• clearAll() resets everything
• toJSON() / constructor hydration round-trip
• isEmpty getter

These are all synchronous, no mocking needed.

---

CRITICAL: _savePersistedFilters is never called

_savePersistedFilters(filterState) is defined in lib/tui/index.cjs but is never called in the keyboard handler wiring shown in the diff. There is no filter-toggle or filter-clear handler that calls it after mutations. Without saves, the persistence feature (one of the stated test plan items) is non-functional.

Expected pattern in each mutating handler:

keyboard.on('filter-toggle', () => {
  filterState.toggleCursor();
  _savePersistedFilters(filterState);
  filtered = _applyFiltersAndSearch();
  draw();
});

keyboard.on('filter-clear', () => {
  filterState.clearAll();
  _savePersistedFilters(filterState);
  filtered = _applyFiltersAndSearch();
  draw();
});

---

filtered variable not updated on filter change

The existing filtered variable is initialized as search.search(query) (searching all issues). When filters are applied via _applyFiltersAndSearch(), the result should replace filtered. But the keyboard handlers need to explicitly reassign filtered = _applyFiltersAndSearch() after any filter mutation. Verify all mutating handlers do this.

---

Merge order dependency on #162

This PR references helpVisible and PAGE_SIZE which are introduced in PR #162. Ensure #162 is merged first. If merged out of order, this PR will fail at runtime.

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Good things

• FilterState class design is excellent — clean cursor model, good section abstraction
• Label AND / Milestone OR filter semantics are explicitly documented and correct
• Persisted filter hydration clamps to available options (prevents stale selections)
• clearAll() correctly resets activeState to 'open' (not 'all')
• toJSON() returning plain arrays (not Sets) is correct for JSON serialization