Release v0.3.0: version bump

[devin-ai-integration]

Summary

Version bump for the v0.3.0 release: mod_version and ide-plugin pluginVersion → 0.3.0, plus a fatJar fix pinning the bundled plugin zip to the current pluginVersion (stale dists in ide-plugin/build/distributions/ could otherwise win the copy). Release v0.3.0 is already published at tag on this head (dbf6b69), matching the established flow.

Link to Devin session: https://app.devin.ai/sessions/f2c11399d60948a394f9836472375e2f
Open in Devin Desktop: https://app.devin.ai/desktop/session/f2c11399d60948a394f9836472375e2f?variant=devin
Requested by: @CommunityPoke

[devin-ai-integration]

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[devin-ai-integration]

Closing as superseded: v0.3.0 was already published (tag v0.3.0), the fatJar plugin-pin fix is already on main via #10, and the current version bump (0.3.1) lives in #11. Resolving this conflict would regress mod_version/pluginVersion to 0.3.0.