feat(sidebar): fold project scope into the search row

[rynfar]

The sidebar used two rows for search and project actions. Search, project scope, New project and New thread now share one row, and the project picker opens beneath the search field. “All projects” stays first when the picker query is empty and disappears while filtering.

Ports every functional hunk from upstream d1d15c67f4a5fb82fd8d5e01e5e3b288296789c3 (#11315); no exclusions. Pylon keeps environment-aware project grouping, project-settings context/keyboard actions, search navigation, clear/refocus and Shift-click creation. The compact scope control includes machine names in its tooltip and accessible label, and stale or negative search indices never produce invalid accessibility references. Related to #526; the owning cycle will consolidate the ledger cursor.

Validation: 196 tests across sidebar logic, pointer behavior, header interactions and environment descriptions; web tsc --noEmit; scoped lint and formatting; clean diff checks. Independent review covered the combined diff and identified the environment-label and negative-index repairs.

Upstream’s original before/after evidence is linked below as a design reference. No local browser or desktop visual pass was run under this task’s authorization.

Upstream before	Upstream after

Implemented with GPT-6 in Codex.

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Project	Deployment	Actions	Updated
pylon-marketing	Ready	Preview	Sep 12, 2026 4:13pm 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	13.9 KiB	−135 B (−0.9%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.2 KiB	7.2 KiB	+12 B (+0.2%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.8 KiB	6.7 KiB	−147 B (−2.1%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	58.8 KiB	58.0 KiB	−866 B (−1.4%)	66.4 KiB	✅
Codex	Live turn messages	9	8	−1 (−11.1%)	21	✅
Claude	Total thread wire	14.1 KiB	13.9 KiB	−169 B (−1.2%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.2 KiB	7.2 KiB	+6 B (+0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.9 KiB	6.7 KiB	−175 B (−2.5%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	59.7 KiB	58.8 KiB	−928 B (−1.5%)	66.4 KiB	✅
Claude	Live turn messages	10	8	−2 (−20.0%)	21	✅

Baseline: 6e879c2 · PR result: ee74ede · 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: 116.4 KiB

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