Add GTFS-RT service alerts to SMS and voice (#8)

[aaronbrethorst]

Closes #8.

Summary

• Surfaces active OneBusAway service alerts ("situations") tied to a queried stop or its routes in both SMS and voice responses. Alerts are read from the REST arrivals-and-departures-for-stop response's references.situations — no new data source, config, or dependency.
• SMS: active alerts are prepended above the arrivals (first page only), each truncated to keep the message short; a "+N more" line covers overflow. Voice: alerts are spoken before arrivals on the initial stop lookup, then the normal arrivals + menu follow.
• Adds an ActiveSituations() model method that filters situations by their activeWindows against the server's currentTime (ms, with defensive seconds→ms normalization; fails open when the server time is unknown). Alert presentation is localized across all 10 supported languages.
• Refactors OneBusAwayResponse's anonymous nested structs into named exported types (OBAResponseData/OBAStopEntry/…) so situation fields could be added cleanly; field-access paths are unchanged.

Scope note: per discussion, this iteration covers alerts tied to a queried stop/route. System-wide disruptions played at the very start of a call (before a stop is chosen) require a separate global source (e.g. a GTFS-RT ServiceAlerts feed) and are deferred to a follow-up issue — the Situation model and formatter layer are built to be reused for it. See spec §8.

How it was built

Spec → context7 review → live verification against api.pugetsound (confirmed activeWindows are ms, field shapes, and that a real alert parses) → implementation plan → plan review → subagent-driven TDD execution (7 tasks, each spec+quality reviewed) → whole-branch review → /simplify. Design docs live under docs/superpowers/.

Test plan

• make fmt, make vet, make lint (0 issues), make test — full suite green (15 packages)
• Unit tests: ActiveSituations active-window filtering (active/expired/future/open-ended/seconds-normalized/fail-open), SMS+voice formatters (caps, overflow, truncation, no-URL-read-aloud), SMS & voice handler injection, locale key parity
• Live smoke against real API (stop 1_75403, which had an active alert):
  • SMS: alert prepended + truncated, then arrivals, then hints
  • Voice: alert spoken first in its own <Say>, then arrivals <Say>, then menu <Gather>
  • Voice "extend departures" loop: alert not repeated (regression-tested)
  • No-alert stops (1_431, 1_13721): output unchanged (no-op verified)

Review notes (non-blocking)

• SMS segment cost: the ⚠ prefix forces UCS-2 encoding and up to 2 alerts × 140 runes can add SMS segments. Left at smsMaxAlerts = 2; dropping to 1 is a one-line lever if segment cost matters.
• Alert body language: OBA emits summary/description in the agency's language (English on Puget Sound); only the lead-in/prefix is localized. Inherent to single-language situation data.
• Deferred follow-up: open a separate issue for system-wide-at-call-start alerts (spec §8).

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Configuration used: Organization UI

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Run ID: 0d48986e-d903-4d74-b47f-51c9ed048ebe

📥 Commits

Reviewing files that changed from the base of the PR and between 8d5bf34 and 438a1c3.

📒 Files selected for processing (27)

• client/onebusaway_test.go
• client/validation_test.go
• docs/superpowers/plans/2026-07-01-service-alerts.md
• docs/superpowers/specs/2026-07-01-service-alerts-design.md
• formatters/alerts.go
• formatters/alerts_test.go
• handlers/disambiguation_test.go
• handlers/sms.go
• handlers/sms_session_test.go
• handlers/sms_test.go
• handlers/voice/find_stop.go
• handlers/voice/find_stop_test.go
• handlers/voice_menu_test.go
• locales/ar-US.json
• locales/de-US.json
• locales/en-US.json
• locales/es-US.json
• locales/fr-US.json
• locales/ko-US.json
• locales/pl-PL.json
• locales/pt-US.json
• locales/ru-US.json
• locales/zh-CN.json
• main_test.go
• models/situation.go
• models/situation_test.go
• models/types.go

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