fix(sms-bridge): enumerate PII-safe static OpenCode error codes

[xnoto]

Summary

• Enumerate PII-safe static error_code values on BridgeError for the
  opencode-sms-bridge's OpenCode stage: opencode-request-failed (HTTP/URL/OSError
  request errors), opencode-response-invalid (invalid or missing response shapes
  and JSON), and opencode-input-invalid (empty prompt text), alongside the
  existing twilio-send-failed and ok outcomes.
• BridgeError now always carries a bounded static error_code, defaulting to
  opencode-response-invalid and coercing any non-bounded value, so unclassified
  failures can never persist or log free-form text.
• process_job logs and persists the bounded error_code in place of the coarse
  opencode-failed detail code. No raw exception text, response/request bodies,
  URLs, session or message IDs, credentials, or provider details appear in logs or
  the persisted detail_code. Unsupported-media behavior is unchanged.
• Focused unit coverage adds the bounded request-error mapping, the safe default
  and coercion, and process_job persistence of the bounded code; all existing
  tests are preserved.

Fixes #

None — owner-requested PII-safety hardening; no driving issue supplied.

Type of change

• Bug fix
• Feature / enhancement
• Documentation
• Infrastructure (OpenTofu root or module)
• GitOps desired state (manifests, kustomize, charts, SOPS/KSOPS secrets)
• Container image
• CI / reusable workflow
• Refactor / cleanup
• Breaking change

Validation

• Required pull-request checks pass — pending at PR creation; the pull-request
  buildah workflow runs pre-commit (including Gitleaks), changed-image detection,
  and the non-publishing bridge image build. Result will be recorded on the PR.
• Generated or centrally distributed files were regenerated by their owning
  automation, not hand-edited — none changed; only opencode-sms-bridge/server.py
  and opencode-sms-bridge/test_server.py were edited.

No local tests, container builds, OpenTofu, SOPS, state, or live-system
operations were run or claimed. CI is the validation authority.

Impact and rollout

Producer changed: makeitworkcloud/images/opencode-sms-bridge is the
canonical bridge-image source. An approved merge automatically publishes a new
immutable GHCR image tag. This PR neither publishes nor deploys anything itself.

Consumer unchanged: kustomize-cluster continues to select its currently
pinned image; this PR makes no GitOps or image-selection change. After an
approved merge and publication, a separate reviewed GitOps PR and explicit
confirmation are required before image selection, Argo reconciliation, health
verification, and a new approved-source SMS test.

Behavior boundary: worker job rows that previously failed with the coarse
opencode-failed detail now persist the bounded opencode-request-failed,
opencode-response-invalid, or opencode-input-invalid code, and the
job_failed log line carries the same error_code. Any consumer of the old
literal opencode-failed value must be updated before relying on the new codes.

Rollback: if a later selected image regresses, use the canonical GitOps
workflow to select a reviewed immutable image tag. Do not overwrite image tags
or alter live state manually.

Safety and secrets

• Contains no plaintext secrets, decrypted SOPS values, state files,
  kubeconfigs, tokens, or private endpoints.
• No local OpenTofu init/plan/apply/destroy/import/state operations were run
  or claimed — plans come from pull-request checks.
• Breaking or irreversible effects are described above with rollback notes.

AI-assisted change: an OpenCode agent materially produced this change; reviewers
should verify the bounded error-code enumeration, the safe default and coercion,
the process_job persistence path, and CI results before merge.

[github-actions]

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