chore: normalize commit messages

[marcus]

Summary

• add a strict repo-level commit-msg hook that only normalizes safe type: prefix casing/spacing and rejects non-(td-<id>) trailing suffixes
• update make install-hooks to install both hooks through git rev-parse --git-path hooks, which works in normal repos and Git worktrees
• align contributor docs and release automation on the canonical type: summary / type: summary (td-<id>) format

Verification

• go build ./...
• go test ./... -run TestCommitMsgHook
• isolated clone + detached worktree dry run: make install-hooks succeeded, Feat : ... (td-2b41b2) normalized to feat: ... (td-2b41b2), and feat: ... (jira-123) was rejected
• go test ./... still fails in pre-existing internal/features tests (TestKnownFeatureDefaults, TestIsEnabledForProcess_EnableDisableLists, TestIsEnabled_ProjectConfigAndEnvPrecedence); this change does not touch that package

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