fix(plugin): bound source preview reads

[mluck-openai]

Summary

Repository ranking currently buffers entire text files to produce short source previews. Limit filesystem preview reads to 64 KiB by default, reusing the existing explicit-file budget.

Changes

• Apply the shared default to repository, directory, explicit-file, and local-patch previews.
• Include the initial binary-detection sample in the read budget and reject nonpositive limits.
• Add large-text read-count regressions and coverage for truncated source, Unicode, binary detection, and overlapping scopes.

Testing

• Focused preview, rank-input, and inventory tests: 152 passed.
• Full Python suite: 1,109 passed, 8 skipped, and 109 subtests passed. One unchanged CLI-help test failed with inherited PYTHONSAFEPATH=1; its isolated rerun passed with that override unset.
• Ruff lint and formatting checks passed.
• TypeScript build:ci, plugin source compatibility checks, and all 9 compatibility-checker tests passed.
• git diff --check passed.

Risk and rollout

Files larger than 64 KiB now produce previews from their prefix; later declarations and binary markers are not inspected. Explicit-file inclusion and the output preview budget are preserved. Committed-revision blob retrieval is outside this change. No release or version bump is included.

Public disclosure review

• No customer, partner, prospect, or user identities, data, or identifying details are included.
• No credentials, personal data, private source, scan findings, or nonpublic links or tickets are included.
• I reviewed the branch name, title, description, commits, changes, comments, logs, screenshots, attachments, and links for public disclosure.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
🔒 Security Review	✅ Completed 2026-09-17T00:42:41.067475Z	b891a7f	Draft marked ready

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