feat: add internal event journal

[minixalpha]

Summary

• Add schema-versioned Native Events and a per-run append-only Event Journal.
• Project the existing text output from the same user, model, tool, and terminal runtime facts without changing CLI output.
• Document the v1 protocol, security boundary, and the future Event Journal-to-ATIF implementation path.

Implementation

• Persist replayable JSONL entries with run IDs, sequence numbers, UTC timestamps, producer provenance, model/tool correlation IDs, usage, durations, provider response metadata, and explicit truncation metadata.
• Store journals under ~/.nanoPyCodeAgent/journals/ with user-only directory and file permissions.
• Preserve complete-line append semantics, tolerate only an interrupted trailing record, and fail closed on invalid schemas, events, JSON values, truncation envelopes, or contradictory tool failures.
• Keep model content discriminator fields replayable even at the minimum truncation limit.
• Measure model duration when the final message and response headers become available, before local normalization.
• Emit and journal run, user, model, streaming delta, tool, completion, and failure events while preserving current stdout behavior.

Documentation

• Add English and Chinese Event Journal protocol v1 documentation.
• Update the bilingual README, 0.8.x dev notes, changelog, and bilingual Event Journal/ATIF research notes.

Testing

• Cover append order, replay, torn tails, permissions, truncation, strict JSON/schema validation, producer provenance, nested model facts, tool exceptions, duration boundaries, and exact stdout projection.
• uv run pytest -q — 165 passed locally.