Phase 3 PR2 of the Regional Intelligence Model. Adds LLM-powered
weekly intelligence briefs per region, completing the core feature set.

## New seeder: scripts/seed-regional-briefs.mjs

Standalone weekly cron script (not part of the 6h derived-signals bundle).
For each non-global region:
  1. Read the latest snapshot via two-hop Redis read
  2. Read recent regime transitions from the history log (#2981)
  3. Call the LLM once per region with regime trajectory + balance +
     triggers + narrative context
  4. Write structured brief to intelligence:regional-briefs:v1:weekly:{region}
     with 8-day TTL (survives one missed weekly run)

Reuses the same injectable-callLlm + parse-validation + provider-chain
pattern from narrative.mjs and weekly-brief.mjs.

## New module: scripts/regional-snapshot/weekly-brief.mjs

  generateWeeklyBrief(region, snapshot, transitions, opts?)
    -> { region_id, generated_at, period_start, period_end,
         situation_recap, regime_trajectory, key_developments[],
         risk_outlook, provider, model }

  buildBriefPrompt()    — pure prompt builder
  parseBriefJson()      — JSON parser with prose-extraction fallback
  emptyBrief()          — canonical empty shape

Global region is skipped. Provider chain: Groq -> OpenRouter. Validate
callback ensures only parseable responses pass (narrative.mjs PR #2960
review fix pattern).

## Proto + RPC: GetRegionalBrief

  proto/worldmonitor/intelligence/v1/get_regional_brief.proto

  - GetRegionalBriefRequest { region_id }
  - GetRegionalBriefResponse { brief: RegionalBrief }
  - RegionalBrief { region_id, generated_at, period_start, period_end,
                    situation_recap, regime_trajectory,
                    key_developments[], risk_outlook, provider, model }

## Server handler

  server/worldmonitor/intelligence/v1/get-regional-brief.ts

Simple getCachedJson read + adaptBrief snake->camel adapter.
Returns upstreamUnavailable: true on Redis failure so the gateway
skips caching (matching the get-regime-history pattern from #2981).

## Premium gating + cache tier

  src/shared/premium-paths.ts + server/gateway.ts RPC_CACHE_TIER

## Tests — 27 new unit tests

  buildBriefPrompt (5): region/balance/transitions/narrative rendered,
                        empty transitions handled, missing fields tolerated
  parseBriefJson (5): valid JSON, garbage, all-empty, cap at 5, prose extraction
  generateWeeklyBrief (6): success, global skip, LLM fail, garbage, exception,
                           period_start/end delta
  emptyBrief (2): region_id + empty fields
  handler (4): key prefix, adapter export, upstreamUnavailable, registration
  security (2): premium path + cache tier
  proto (3): RPC declared, import wired, RegionalBrief fields

## Verification

- npm run test:data: 4651/4651 pass
- npm run typecheck + typecheck:api: clean
- biome lint: clean

P2 #1 — no consumer surface for GetRegionalBrief

Acknowledged. The consumer is the RegionalIntelligenceBoard panel,
which will call GetRegionalBrief and render a weekly brief block.
This wiring is Phase 3 PR3 (UI) scope — the RPC + Redis key are the
delivery mechanism, not the end surface. No code change in this commit;
the RPC is ready for the panel to consume.

P2 #2 — readRecentTransitions collapses failure to []

readRecentTransitions returned [] on Redis/network failure, which is
indistinguishable from a genuinely quiet week. The LLM then generates
a brief claiming "no regime transitions" when in reality the upstream
is down — fabricating false input.

Fix: return null on failure. The seeder skips the region with a clear
log message when transitions is null, so the brief is never written
with unreliable input. Empty array [] now only means genuinely no
transitions in the 7-day window.

P2 #3 — parseBriefJson accepts briefs the seeder rejects

parseBriefJson treated non-empty key_developments as valid even if
situation_recap was empty. The seeder gate only writes when
brief.situation_recap is truthy. That mismatch means the validator
pass + provider-fallback logic could accept a response that the seeder
then silently drops.

Fix: require situation_recap in parseBriefJson for valid=true, matching
the seeder gate. Now both checks agree on what constitutes a usable
brief, and the provider-fallback chain correctly falls through when
a provider returns a brief with developments but no recap.

…ptile P1+P2 on #2989)

P1 — TTL silently not applied (briefs never expire)

Upstash REST ignores query-string SET options (?EX=N). The correct
form is path-segment: /set/{key}/{value}/EX/{seconds}. Without this
fix every brief persists indefinitely and Redis storage grows
unboundedly across weekly runs.

P2 — seed-meta not written when all regions skipped

writeExtraKeyWithMeta was gated on generated > 0. If every region
was skipped (no snapshot yet, or LLM failed), seed-meta was never
written, making the seeder indistinguishable from "never ran" in
health tooling. Now writes seed-meta whenever failed === 0,
carrying regionsSkipped count.

P2 #3 (validate gate) — already fixed in previous commit (parseBriefJson
now requires situation_recap for valid=true).

…view P2 on #2989)

…cycle (review P2 on #2989)

… P2 on #2989)