Batch merge: PRs #68, #58, #59, #61, #60, #62, #57, #56

[mattleaverton]

Summary

Batch merge of 8 open PRs with conflict resolution. All tests pass, build is clean.

Included PRs (original commits preserved with author attribution)

• fix(ci): gofmt cli_only_models_test and run-scope demo dot paths #68 (leegonzales) — gofmt cli_only_models_test + run-scope demo dot paths
• attractor: emit AssistantMessage turns for API session events #58 (brianfeucht) — emit AssistantMessage turns for CXDB
• feat(cli): add --validate alias for --preflight in attractor run #59 (mvanhorn) — add --validate alias for --preflight
• fix(engine): tighten input reference scanning to reduce false matches #61 (mvanhorn) — tighten input reference scanning to reduce false matches
• fix(engine): emit heartbeat on interval regardless of output growth #60 (mvanhorn) — emit heartbeat on interval regardless of output growth
• fix(engine): add degraded_success status and verification reporting #62 (mvanhorn) — add degraded_success status and verification reporting
• fix(engine): harden fallback status ingestion diagnostics and retry classification #57 (vadimcomanescu) — harden fallback status ingestion diagnostics and retry
• fix(engine/runtime): enforce run ownership locking and scrub inherited stage contract env #56 (vadimcomanescu) — run ownership locking and env scrubbing

Conflict resolution

All 4 mvanhorn PRs and PR #68 shared cleanup commits that conflicted with the already-merged #67 (GPT-5.4-SPARK model rename). Each merge conflict was the same trivial resolution: keep the renamed model ID with corrected gofmt whitespace.

Verification

• go build ./... — clean
• go test ./... — all packages pass

⚠️ Must merge with "Create a merge commit" strategy to preserve individual contributor commit authorship.

Closes #68, closes #58, closes #59, closes #61, closes #60, closes #62, closes #57, closes #56