fix: skip framework download when already at latest version

[montfort]

Summary

• Add semver version comparison in update-framework before downloading, matching the pattern already used by update-cli in self_update.rs
• Without this fix, every devtrail update re-downloads and overwrites all 65 framework files even when the installed version matches the latest release

Test plan

• cargo build — compiles clean
• cargo test — 25 tests passing
• Verified version comparison chain: checksums.version ("fw-2.1.0") → strip_tag_prefix ("2.1.0") → semver parse → correct comparison

🤖 Generated with Claude Code

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