fix(release): overwrite existing artifacts on re-run

[sairus2k]

Problem

The v0.1.15 release failed at the homebrew formula step on an expired TAP_GITHUB_TOKEN — after the GitHub release and all five assets had already published.

Re-running after refreshing the token failed earlier, at asset upload:

scm releases: failed to publish artifacts: failed to upload glmt_0.1.15_linux_amd64.tar.gz:
422 Validation Failed [{Resource:ReleaseAsset Field:name Code:already_exists}]

scm releases runs before homebrew formula, so goreleaser aborted without ever retrying the step that actually failed. Recovering meant deleting all five published assets by hand, then re-running.

Fix

release.replace_existing_artifacts defaults to false. Setting it true makes goreleaser remove a conflicting artifact and retry — but only when an upload fails because it already exists, so a normal release pays nothing for it.

Any future release that dies after publishing assets — expired credential, tap outage, rate limit — becomes recoverable with a plain gh run rerun --failed.

Note

Because release.yml checks out the tag, this only takes effect for tags cut after it merges. It does not change re-runs of v0.1.15.

Verification

v0.1.15 is fully published and the tap is updated, recovered manually via the delete-and-rerun path this change automates:

• Release: all 5 assets present
• sairus2k/homebrew-tap → version "0.1.15"
• Formula sha256 values match the published checksums.txt exactly, so brew install verifies