feat(atif): add Harbor ATIF trajectory format support

[jfeldstein]

Currently

Euphony renders Harmony conversations and Codex JSONL session logs, with a dedicated <euphony-codex> viewer for the latter. Harbor's Agent Trajectory Interchange Format (ATIF) — a single-document JSON format that's structurally distinct from both — is not detected and falls through to the generic JSON viewer, which loses the trajectory-specific rendering (tool-call ↔ observation pairing, agent metadata, step metrics, etc.). Loading a *.trajectory.json from harbor/tests/golden/... today shows raw JSON with no conversational structure.

Change Summary

• New src/utils/atif-trajectory.ts: schema types, isAtifTrajectory detector, parseAtifTrajectory (ATIF → Conversation), serializeAtifTrajectory round-trip, and validateAtifTrajectory. Steps map to one primary dialogue message plus optional reasoning, tool-call, and observation messages. Tool calls and their matching observations correlate by function_name (built from a per-step tool_call_id → function_name map) so the viewer renders the call/output pair under a single tool label.
• New <euphony-atif> Lit shell that mirrors <euphony-codex> and delegates to <euphony-conversation>. Read-only by design (no is-editable property forwarded).
• New src/components/app/local-data-parser.ts: extracted the inline parser out of local-data-worker.ts so it's unit-testable. ATIF detection runs before the Codex JSONL check.
• src/components/app/app.ts: DataType.ATIF, state field, render branch, and URL-load branch.
• Validator mirrors harbor's Pydantic constraints: sequential step_id, agent-only fields, ContentPart shape (text/image required fields, image media_type literal), tool-call ↔ observation source_call_id references, strict ISO-8601 timestamps, tool_definitions envelope shape.
• Tests: src/utils/atif-trajectory.test.ts (12 cases) and src/components/app/local-data-parser.test.ts (6 cases) — both run under vitest.

Acceptance Criteria

• pnpm test — vitest passes (18/18)
• pnpm build — clean
• Load a Harbor ATIF trajectory via URL (?path=https://...) → renders with Session/Agent/Schema/Steps chips and tool-call/output pairs sharing a label
• Regular Conversation JSON still routes correctly (verified: examples/simple-harmony-convos.jsonl → dataType=conversation → <euphony-conversation>)
• Codex JSONL still routes correctly (verified: minimal session_meta/event_msg/response_item JSONL → dataType=codex → <euphony-codex>; ATIF detection runs first but only matches single-element arrays whose first element looks like an ATIF document)
• Round-trip integrity: serializeAtifTrajectory(parseAtifTrajectory(x).conversation) deep-equals x for all harbor goldens (8/8 terminus_2 fixtures + 2/2 openhands *.trajectory.json fixtures, all v1.5/v1.6, deep-equal)
• Routing matrix: every *.trajectory.json in harbor/tests/golden/{terminus_2,openhands} routes to DataType.ATIF and mounts <euphony-atif> (10/10); both *.traces.json files (raw OpenHands replay events, not ATIF) correctly fall back to DataType.JSON
• Load via "Load local file" — manually checked by me, Jordan

Notes

• Read-only by design. <euphony-atif> does not expose is-editable, and ?disable-editing-mode-save-button=${true} is set as belt-and-suspenders. serializeAtifTrajectory returns the originally-parsed document verbatim — it does not synthesize ATIF from edits to the in-memory Conversation, because the schema requires sequential step IDs, agent name/version, and tool-call/observation ID references that arbitrary Harmony conversations don't reliably preserve. If lossy export of edited trajectories ever becomes a requirement, build a separate writer rather than changing this one.
• Detection ordering. ATIF runs before Codex JSONL detection. ATIF is a single JSON document (one-element array after JSON.parse), so the discriminator is cheap and unambiguous (schema_version: "ATIF-*" + agent.{name,version} + non-empty steps). Putting it first prevents a future ATIF version with an event-shaped extra field from being misclassified as Codex.
• Validator strictness vs. harbor. Harbor's Pydantic types tool_definitions only as list[dict[str, Any]] but the RFC text mandates the OpenAI {type, function} envelope; we enforce the RFC. Image media_type is restricted to the four-MIME Literal harbor uses. Strict ISO-8601 timestamp regex matches Step.validate_timestamp in harbor/src/harbor/models/trajectories/step.py; the parser uses the same check so a timestamp that fails validation also yields create_time === undefined rather than a Date.parse-coerced value.