BRO-034: loading state — address bar goes yellow-bg/black-text while a verb runs

Now: DONE
Sev: LOW

Input

Context

Feature (gritzko 2026-07-18): before loading something (click, spell, refresh — any verb the pager drives), repaint the address bar black-on-yellow so the user KNOWS a load is in flight; restore the normal bar style when the view arrives (or the error paints red).

The pager is single-threaded around the verb call — the yellow paint must land on the terminal BEFORE the verb runs, not queue behind it.
The banner theme already has a black-on-pale-yellow band (THEME_BANNER, the C HUNKu8sFeedBanner style) — reuse the palette, don't invent a new pair.

Goals

Every pager-driven load shows the yellow bar for its duration.

Paint on: click nav, :spell verbs, R refresh, -/back replays; write-through + flush before invoking the verb.
Clear on: view swap (normal bar), error (existing red), including the no-hunks path.
Instant loads just flicker — acceptable; no timers, no spinner, no async machinery.

Constraints

views/bro only (theme.js + the address-bar drawer + the call sites in pager.js); no verb/loop changes.
Style via the theme table, not inline SGR literals.
pty leg: capture the yellow bar mid-load (a deliberately slow verb or big tree), and its clearing on arrival + on error.

WIP

Design decisions

(pending)

TODOs

theme entry (reuse banner palette) + bar drawer "loading" mode
paint+flush before driveSpell/refresh call sites; clear on swap/error
pty legs: mid-load capture, clear-on-arrival, clear-on-error

Blockers and bummers

(none yet)

Outcome

(pending)