ci(lint): lint the full tree, not just the diff

[krisarmstrong]

Summary

Drop --new-from-rev=HEAD~1 from the golangci-lint step so CI lints the whole tree instead of only changed lines. The pre-existing backlog that blocked this earlier is gone — a full-tree golangci-lint v2.12.2 run on origin/main reports 0 issues, so "zero warnings" now truly means the whole repo.

Linked Issue

Related to #1738

Testing Evidence

golangci-lint run ./...   (full tree, origin/main, v2.12.2) -> 0 issues.

Security and Release Checklist

• No secrets, tokens, credentials, or customer data are included.
• Mutating routes, auth surfaces, permission checks, and output encoding were reviewed if touched.
• Dependencies are pinned and justified if changed.
• Documentation, screenshots, or operator notes were updated if behavior changed.

[github-actions]

📋 License Compliance Report

✅ All dependencies pass license compliance checks

Go Dependencies

• Unknown: 118 package(s)
• MIT: 30 package(s)
• BSD-3-Clause: 17 package(s)
• Apache-2.0: 12 package(s)
• BSD-2-Clause: 2 package(s)

npm Dependencies

See full report in workflow artifacts

Allowed Licenses: MIT, Apache-2.0, BSD-*, ISC, CC0-1.0, MPL-2.0
Forbidden: GPL, AGPL, SSPL (strong copyleft)