Prepare dev.kit 0.20.1 context scaffold fixes

[fqjony]

Summary

• exclude gitignored root YAML files from declared contract manifest discovery
• seed missing .rabbit/README.md files so new repos have a Rabbit-facing notes surface without adding a generic docs/README.md stub
• reserve 0.20.1 for the next patch release

Context

These follow up on post-merge Copilot comments on PR #29 plus the worker-php follow-up that moved Rabbit CI notes under .rabbit/README.md. They are not critical for the already published 0.20.0 release, but should be included in the next patch release.

Validation

• bash tests/suite.sh --only repo-contract
• bash tests/suite.sh --only core
• make test
• git diff --check

[Copilot]

Pull request overview

This PR prepares the repo for the post-0.20.0 patch release by tightening declared root YAML contract manifest discovery to respect gitignore-aligned file filtering, and by improving the default repo scaffold to include a Rabbit-facing README in .rabbit/.

Changes:

• Update root YAML manifest discovery to use repo “content files” filtering (so gitignored root YAML isn’t promoted into generated context).
• Add scaffolding for .rabbit/README.md (and add/adjust tests to ensure it’s created only when missing and never overwrites an existing one).
• Bump version metadata to 0.20.1 and document the release in changes.md.

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/suite.sh	Adds regression coverage for excluding gitignored root YAML manifests; validates .rabbit/README.md scaffolding behavior.
lib/modules/repo_scaffold.sh	Seeds .rabbit/README.md if missing; changes declared root YAML discovery to use repo file filtering.
package.json	Bumps package version to 0.20.1.
package-lock.json	Syncs lockfile version metadata to 0.20.1.
changes.md	Adds 0.20.1 release notes describing the follow-ups.
.rabbit/README.md	Adds a Rabbit-facing README stub for this repo.
.rabbit/context.yaml	Updates generated context metadata to 0.20.1.

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 9 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 9 changed files in this pull request and generated no new comments.