chore(release): prepare v0.3.0

[chaliy]

What

Prepare release v0.3.0.

• Bumps workspace version 0.2.0 → 0.3.0 (root Cargo.toml)
• Updates fetchkit-cli internal pin to fetchkit = "0.3.0"
• Updates Cargo.lock
• Adds the [0.3.0] - 2026-05-18 section in CHANGELOG.md with Highlights + 40 PR entries

Why

40 commits have landed on main since v0.2.0: fetcher security hardening, several feat() enhancements (YouTube transcripts, Wikipedia redirect resolution, HackerNews timestamps, ArXiv PDF indication, RSS content-type detection), tool JSON contract fixes, and a dependency refresh including major bumps for the optional bot-auth feature (sha2 0.11, rand 0.10). Minor version bump per SemVer; no breaking changes.

How

Followed specs/release-process.md: updated changelog + workspace version + internal pin, then ran the release verification commands.

Risk

• Low. Release prep only; no behavior changes.
• CI will create the v0.3.0 GitHub Release on merge and then publish fetchkit and fetchkit-cli to crates.io.

Checklist

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace
• RUSTDOCFLAGS="-D warnings" cargo doc --workspace --no-deps
• cargo build --workspace --exclude fetchkit-python --release
• CHANGELOG updated with Highlights + What's Changed
• Internal fetchkit-cli dep pinned to 0.3.0

Changelog excerpt

Highlights

• Hardened outbound fetch policy across every built-in fetcher: SSRF safeguards, body-size caps, redirect re-validation, and symlink-escape protection
• Bot-auth headers are re-signed on every redirect hop so authenticated fetches survive policy-validated hops
• Enhanced fetchers: YouTube transcript extraction, Wikipedia redirect resolution, HackerNews timestamp display, ArXiv PDF binary indication, RSS content-type detection with HTML-to-Markdown
• Tool JSON contract now exposes conditional-fetch and quality fields (word count, redirect chain, paywall) in the output schema
• Dependency refresh including major bumps for the optional bot-auth feature (sha2 0.11, rand 0.10)

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