fix(read): prioritize known text extensions

[original4422]

Summary

• Treat known text extensions as authoritative before content sniffing, preventing embedded magic-byte literals from turning source files into image/PDF payloads.
• Preserve infer detection for unknown and extensionless files and preserve the existing extension fallback.
• Exercise the real ForgeFsRead path and MIME compatibility matrix with same-file regression tests.

Root cause

infer::get scans the entire supplied buffer and recognizes the %PDF sequence at byte offset 449. Limiting the buffer to the issue's suggested 1 KiB would still include that sequence and therefore would not fix this reproduction. The minimal reliable fix is to trust the existing known-text extension allowlist before content sniffing.

Validation

• cargo test -p forge_services tool_services::fs_read::tests -- --nocapture — 28 passed
• cargo test -p forge_services — 216 passed; doc tests passed
• cargo check -p forge_services — passed
• cargo clippy -p forge_services --all-targets --all-features -- -D warnings — passed
• cargo fmt -p forge_services -- --check — passed
• git diff --check — passed

cargo insta test was unavailable because the local cargo-insta command is not installed, so the complete crate suite was run directly with cargo test. A workspace-wide clippy attempt stopped while building the untouched forge_repo crate because local protoc is absent; CI installs protoc, and the touched crate's all-target/all-feature clippy is green.

Fixes #3812

Co-Authored-By: ForgeCode noreply@forgecode.dev

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[CLAassistant]

All committers have signed the CLA.

[original4422]

Hi @tusharmath, when you have a chance, would you mind reviewing this MIME-detection fix and letting me know if any changes are needed? Thank you!

Co-Authored-By: ForgeCode noreply@forgecode.dev

[github-actions]

Action required: PR inactive for 5 days.
Status update or closure in 10 days.

[original4422]

Status update: this PR is still active and ready for review. The current head remains c8f0320e721b4adaf0bd889c1f7f60456f6f295a and GitHub reports it mergeable.

Validation recorded for this unchanged head includes 28/28 focused fs_read tests, 216/216 forge_services tests, plus passing crate cargo check, all-target/all-feature clippy, and formatting. CLA Assistant confirms all committers have signed. The ci, Bounty Management, and autofix.ci runs remain at the external-contributor action_required gate with zero jobs, so there is no actionable test failure log; Release Drafter passed.

Maintainers, could you please review this when available and approve the gated workflows if appropriate? Thank you.

Co-Authored-By: ForgeCode noreply@forgecode.dev