feat(web): add bounded route history shortcuts on desktop

[rynfar]

Desktop users can move through Pylon routes with Mod+[ and Mod+]. The shortcuts use TanStack Router history, stop Back at the first route seen in this app session, and only move Forward through observed app entries. Router PUSH discards an old forward branch while REPLACE preserves it. Focused editors, terminals, previews, and the model picker keep their keys.

Browser tabs retain their native bracket history shortcuts. Custom nonnative browser bindings for the navigation commands can still move within observed Pylon history. After a reload, forward entries from the earlier app session remain unavailable to these custom commands until Pylon observes them again.

Source: T3 Code 829af7b73a960d390a0b32becd37ad6483627aa4, adapted to Pylon's routing and browser shortcut ownership.

Validation: 115 focused keybinding/navigation tests; web typecheck; scoped lint (one pre-existing AppSidebarLayout React warning); formatting and diff check. Independently reviewed at staged diff 8ecd92b6a6af9de57359a8544ca5956a67f63a7c9af2eaf8077c158885790a98. No browser runtime verification.

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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	13.9 KiB	−38 B (−0.3%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.2 KiB	7.2 KiB	+11 B (+0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.8 KiB	6.7 KiB	−49 B (−0.7%)	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	13.9 KiB	−40 B (−0.3%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.2 KiB	7.2 KiB	−20 B (−0.3%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.7 KiB	6.7 KiB	−20 B (−0.3%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	58.9 KiB	58.9 KiB	−44 B (−0.1%)	66.4 KiB	✅
Claude	Live turn messages	10	9	−1 (−10.0%)	21	✅

Baseline: 7ed3f71 · PR result: e042f22 · 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: 115.7 KiB
• Claude decoded thread snapshot: 116.3 KiB

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

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Project	Deployment	Actions	Updated
pylon-marketing	Ready	Preview	Sep 25, 2026 5:14am UTC

[rynfar]

Synced this PR with current pylon after #791. The keybindings guide now documents both desktop numbered shortcuts and route-history commands; the default binding rules compose without code conflicts. Verified the merged tree with 120 focused keybinding/history tests and the web typecheck. Exact-head CI is now running.