C2 · Geo lat/lng B-tree indexes (PR2)

You are being dispatched from flower Brief #250: C2 · Geo lat/lng B-tree indexes (PR2)

Recall pointer:
- Use recall_brief with id 250 for the full folder if you need provenance.

Target:
- project: lounge (/Users/mikeferrara/Documents/code/lounge)
- branch: feature/authors-optimization
- worktree: not specified
- kind: fresh

Current brief spec:
(no spec yet)

This is a direct request, not a fully-specced plan. If it's clear, resolve it. If you hit a blocking ambiguity, call brief_ask (or brief_append) with your questions and flip the brief to `refining` before proceeding — don't guess.

Recent/key trace events:
[1] participant_joined lounge-refine: (no body)
[2] note_added lounge-refine: Child of /authors optimization epic (#239). Build in `feature/authors-optimization` worktree.

Implement **PR2** (doc 10 §4): add B-tree indexes `locations (lat, lng)` + `cities (lat, long)` (INPLACE, LOCK=NONE, off-peak). Turns the 423ms proximity bounding-box scan into a ~1ms latitude-band scan; unblocks proximity (C7). Migration only, independent (no deps).

Validation: `EXPLAIN` the Dallas bounding box → `range` access on `locations_lat_lng_index` (leading `lat`), not full scan; ~1–3ms vs 423ms.
[3] parent_set lounge-refine: Grouped under epic #239.
[4] status_change lounge-refine: (no body)

Recommended linked context:
{
    "todos": [],
    "scratchpads": []
}

Execution notes:
- Treat the brief as the source of truth.
- Keep work scoped to this dispatch request.
- Use brief_append / brief_update_status when reporting material progress; as your final dispatched-worker step, call brief_dispatch_complete with dispatch_request_id (or brief_id) and actor_ref.
- Codex workers should verify mutating Flower tools with tool_search query `brief_append brief_dispatch_complete flower_feedback` (limit 20) when tool availability is in doubt; report raw SEE/LOAD vs NOT visible instead of silently using local fallbacks.
- Add a git commit trailer `Brief: #250` to every commit for this brief so flower can exact-link commits back to the brief.
- Need an operator call while working this brief? A question ABOUT THIS BRIEF -> brief_ask(250, ...); a standalone decision not tied to the brief -> decision_ask(...). Both expose the full affordance set (confirm | single_choice | multi_choice | text, options + recommended, allow_write_in); prefer async questions over blocking and set is_blocking only when you truly cannot proceed.