tracking(desktop): clear common-path defects and renderer performance debt

[Astro-Han]

Goal

The primary path (create Session → type → read the stream → switch Session → change model or permission mode) has no visible defect and stays responsive on long transcripts.

Common-path defects

• fix(desktop): archived sessions can remain selected and trigger Skills and Plan queries #4430 archived Sessions remain selected and trigger Skills and Plan queries
• Permission mode switch (Auto→Bypass) is not honored by the next turn #3349 permission mode switch Auto → Bypass is not honoured by the next turn
• Default-model picker in Settings spins on every switch #3827 default-model picker in Settings spins on every switch
• The Goal chip reads "running" while an armed Goal waits for its first Turn #3362 Goal chip reads "running" while an armed Goal waits for its first turn
• fix(desktop): connection base URL gate is looser than the Runtime Host contract, so a rejected endpoint reports a misleading error #3672 connection base-URL gate is looser than the Runtime Host contract and reports a misleading error
• fix(desktop): agent graph appears frozen while 0/7 operators are running (no heartbeat) #3878 agent graph appears frozen while 0/7 operators are running
• Failed turns hide the provider's own response; show it collapsed, expandable, for every failure class #4502 failed turns hide the provider's own response; show it collapsed for every failure class

Renderer performance

• bug(ui): upward scroll can snap back to the live tail during geometry changes #4269 upward scroll snaps back to the live tail during geometry changes (PR perf(desktop): bound rendering within oversized turns #4259 by liugddx is in review; the moved guard shape is still open)
• perf(ui): oversized single Turn defeats transcript render bounds #4256 an oversized single Turn defeats transcript render bounds (same PR)
• perf(desktop): make session data flow incremental and bounded #2913 make session data flow incremental and bounded (M4n5ter)
• WorkHub Coordination transcript is replayed in full on every open and every reconnect #4647 WorkHub Coordination transcript is replayed in full on every open and reconnect
• feat(desktop): preserve transcript continuity across bounded ranges #4123 preserve transcript continuity across bounded ranges
• flaky(e2e): transcript-scroll:498 asserts the tail before a viewport change re-pins it #4648 flaky e2e: transcript-scroll asserts the tail before a viewport change re-pins it
• Establish a perf budget in apps/desktop/e2e/native-transcript-perf.spec.ts: first paint of a 500-turn Session, scroll LoAF, switch latency; fail CI on regression.

Rules

• One issue per PR; each PR links back here and states how it was verified (e2e, Storybook, or CDP trace).
• Fixes land on the authority named in the issue; no renderer-side workaround for a Host contract gap.

[Astro-Han]

take