Make deferred mobile navigation feel immediate

[brsbl]

Human comments

What was wrong

Deferred route navigation could appear inert, and a cold thread route could begin without metadata even though the persisted sidebar bootstrap already contained a usable thread placeholder.

What changed

• Show route-progress feedback only after a 120ms delay, then keep it visible for at least 320ms so quick routes do not flash and slow routes do not feel ignored.
• Seed cold thread queries from the in-memory or persisted sidebar bootstrap before the full response arrives.
• Keep indicator colors derived from the active theme anchors.

No mobile-home layout, compact shelf, provider-discovery, or right-panel presentation changes in this layer.

How you verified

• The original behavior capture used Chrome for Testing 151.0.7922.71 at 393×852 CSS px, DPR 2, against exact feature revisions e1b749660fb19ecc402799cfbbaa1cd887ac0188 and ac97a215cb1db1640f11a2de60e9bf2b97d3a70a. The direct layer remains unchanged at current exact base 0eb3bef25c3589f2b3f40cdcb80b20cff131512a and exact head 1b8c66d38227299d70e3033bac8a2f2af35c294d.
• Held the real thread/environment requests pending, clicked the same production recent-thread anchor, and captured at 220ms. The base route had only an anonymous skeleton; the head had already reconstructed the real Wire up automations CLI header and production follow-up composer from persisted sidebar data.
• Assertions and captures targeted the routed header/composer subtrees, not document.body.innerText.
• Remote CI passed the timing tests, typecheck, lint, package smokes, and version gates on the exact final head. No local CI-equivalent command was run.

Before — no cold-route identity	After — immediate production placeholder

BB-Thread-ID: thr_wftu7bh9ez

AGENT GENERATED