Fix explicit td release-notes ranges

[marcus]

Summary

• cherry-pick the release-notes MVP implementation onto a fresh branch from main
• fix td release-notes --range ... so default --to HEAD does not conflict unless --to was explicitly provided
• add command-level regression coverage for explicit ranges and keep the existing docs/workflow updates from the MVP branch

Testing

• go test ./internal/git ./internal/release ./cmd
• go test ./...
• go run . release-notes --range v0.44.0..HEAD --output markdown
• go run . release-notes --output markdown

Notes

• go test ./... still fails in internal/features with pre-existing TestKnownFeatureDefaults, TestIsEnabledForProcess_EnableDisableLists, and TestIsEnabled_ProjectConfigAndEnvPrecedence failures unrelated to this change.

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Automated by nightshift