Replace custom site and option pickers with pi-tui SelectList

[youknowriad]

Related issues

How AI was used in this PR

AI explored the codebase, designed a refactoring plan to adopt pi-tui's SelectList component, and implemented the changes. The plan identified that SelectList already handles list rendering, scrolling, keyboard navigation, and selection — eliminating the need for custom implementations. AI built in custom logic for features SelectList doesn't cover (tab switching, contains-based filtering, browser-open-on-tab).

Proposed Changes

• Site picker: Replaced ~100 lines of custom list rendering (formatSiteRow, getSitePickerRows, getVisibleWindow, getScrollInfo, sitePickerPageSize) with SelectList. Maintains custom tab switching (local/WordPress.com), contains-based search filtering, and tab-to-open-browser.
• Option picker: Replaced ~30 lines of manual up/down/enter navigation with SelectList's built-in handling.
• Editor bottom bar: Added showBottomBar flag to hide hint/status line while site picker is visible, reducing visual clutter.
• Input routing: Refactored to forward navigation keys (up/down/enter) to SelectList while keeping custom keys (tab/left/right/escape/backspace/chars) for site picker features.
• Filtering: Inlined getFilteredSitePickerItems() into rebuildSitePickerList() to avoid indirection; SelectList is recreated on every query change with pre-filtered items (working around SelectList's prefix-only filtering).

Testing Instructions

1. Run npm run cli:build && node apps/cli/dist/cli/main.js ai
2. Press down arrow to open site picker
3. Verify navigation (up/down arrows move selection, → switches to WordPress.com, ← back to local)
4. Verify search (type letters to filter, backspace to delete, esc to clear query)
5. Verify selection (enter to select, tab to open in browser)
6. Verify visual alignment: [Local] tab and → indicator should align with prompt text
7. Verify spacing: empty line between tab header and list, between search line and list

Pre-merge Checklist

• TypeScript typecheck passes
• Tests pass (21 tests in cli/ai)
• Linting passes
• Manual testing of site picker navigation, filtering, selection, and tab switching

[wpmobilebot]

📊 Performance Test Results

Comparing 60e545e vs trunk

app-size

Metric	trunk	60e545e	Diff	Change
App Size (Mac)	1279.98 MB	1279.98 MB	0.01 MB	⚪ 0.0%

site-editor

Metric	trunk	60e545e	Diff	Change
load	1893 ms	1985 ms	+92 ms	🔴 4.9%

site-startup

Metric	trunk	60e545e	Diff	Change
siteCreation	7088 ms	7145 ms	+57 ms	🔴 0.8%
siteStartup	3922 ms	3925 ms	+3 ms	⚪ 0.0%

---

Results are median values from multiple test runs.

Legend: 🟢 Improvement (faster) | 🔴 Regression (slower) | ⚪ No change (<50ms diff)

[taipeicoder]

@youknowriad I get stuck when first switching to remote sites, then about 3 minutes later the message "Not logged in. Use /login first." shows up.

[youknowriad]

What's the expected outcome when switching to remote sites, since we don't have copy...?

[taipeicoder]

I think the next step would be to copy the remote site locally and then be able to push it. Currently it's functionless.

[youknowriad]

I get stuck when first switching to remote sites, then about 3 minutes later the message "Not logged in. Use /login first." shows up.

I don't reproduce this btw.

[youknowriad]

My guess is that we may not handle expired tokens properly or things like that but it seems to be out of scope of the current PR.