fix(repo): preserve JSONL line endings

[U1oSun]

Summary

• Preserve LF line endings for .jsonl files across Windows, macOS, and Linux checkouts.

Why

• Issue/Story: justified repository maintenance, extracted from the maintainer-approved standalone follow-up discussed in feat(harness): add task-scoped experience traces #77.
• User or maintainer outcome: byte-sensitive JSONL artifacts are not rewritten to CRLF on Windows checkout.

Traceability and Scope

• Spec/ADR, if applicable: not applicable; this is a one-line repository metadata fix.
• Acceptance criteria addressed: git check-attr resolves .jsonl as text with eol=lf.
• Canonical owners changed: .gitattributes
• Explicit non-goals: no Experience Trace implementation, schema, CLI, packaging, or runtime changes.

Change Type

• Bug fix
• New feature
• Refactor
• Documentation
• Tests
• CI or repository maintenance

Test and Review Evidence

Check	Result
git check-attr --all -- sample.jsonl	text: set; eol: lf
git diff --check	passed
npm run pack:verify	passed; npm 499 entries, runtime zip 521 entries
npm test	1,310 total; 1,307 passed, 1 failed, 2 skipped. The failure is the current main Windows reporter-path test at test/governance/test-ci-reporting.test.mjs:57 and is unrelated to .gitattributes.

Manual or visual evidence: the compare view contains one file and one added attribute rule.

Risk and Recovery

• Compatibility and cross-platform impact: Git keeps tracked .jsonl files on LF checkouts across supported platforms.
• Package, plugin, schema, or generated-file impact: none.
• Rollback or recovery path: revert commit 4f9538f.
• Residual risk or unverified boundary: current main contains no tracked .jsonl files; this rule establishes behavior for future JSONL artifacts.

AI Involvement

Level: Assisted.

Human review and validation: contributor directed the scope; Git attributes and repository checks were reviewed before submission.

Checklist

• I followed AGENTS.md and CONTRIBUTING.md.
• I ran focused tests or checks for the changed behavior.
• Tests and documentation match the final behavior.
• Markdown links and generated documentation are current.
• I considered Windows, macOS, and Linux behavior.
• Package verification was run for packaging-sensitive paths.
• Not applicable: this does not change commands, output, installation, compatibility, or a public extension contract, so no CHANGELOG entry is required.
• I have the right to contribute this work under the repository license.