feat(web): choose themes from command palette

[rynfar]

What changed

The command palette now offers Change theme with color previews and Change appearance with System, Light, and Dark choices. A theme choice writes through Pylon's existing theme preferences; single-appearance themes affect only their matching half, as they do in Settings. The new shortcuts open the theme picker or cycle appearance outside terminal focus. Pylon's first-run setup action and mobile-only appearance guidance remain intact.

This is an adapted port of upstream 9686cd9afe20d13fcb850199f9b9849a8276737a. It adds a shortcut to the existing web/desktop theme system, without changing mobile theme ownership or provider commands.

Validation

• 188 focused tests across command palette, keybindings, theme palette, theme hook, and contract schema.
• Web typecheck passed. Scoped lint passed with existing effect-state warnings and one new matching layout-effect warning for the one-shot palette intent. Formatter and diff checks passed.
• Independent source review passed. No live browser or keyboard-device verification was performed.

Model: GPT-6 Sol (low) via Codex harness, with root agent oversight.

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Project	Deployment	Actions	Updated
pylon-marketing	Ready	Preview	Sep 25, 2026 5:54am UTC

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	14.0 KiB	14.0 KiB	−24 B (−0.2%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.2 KiB	7.2 KiB	+8 B (+0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.8 KiB	6.7 KiB	−32 B (−0.5%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	58.0 KiB	58.0 KiB	−44 B (−0.1%)	66.4 KiB	✅
Codex	Live turn messages	10	9	−1 (−10.0%)	21	✅
Claude	Total thread wire	14.0 KiB	14.0 KiB	+8 B (+0.1%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.2 KiB	7.2 KiB	−11 B (−0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.7 KiB	6.8 KiB	+19 B (+0.3%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	58.9 KiB	58.9 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	10	10	0 (0.0%)	21	✅

Baseline: 7ed3f71 · PR result: c074da5 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 115.6 KiB
• Claude decoded thread snapshot: 116.3 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.