chore: Remove yarn setup, rely on npx for @appland/appmap

[dividedmind]

package.json and yarn.lock only served the rake install task used in the dev/test environment. Since npx resolves @appland/appmap at runtime anyway, the yarn layer adds no value.

[Copilot]

Pull request overview

This PR removes the Yarn-based Node dependency setup (previously used to install @appland/appmap) and shifts the project to relying on runtime npx resolution instead, with corresponding documentation and CI updates.

Changes:

• Remove package.json and yarn.lock and delete the rake install task that ran yarn install.
• Update Rakefile test task dependencies so spec depends only on compile.
• Update CI/docs to reflect removal of Yarn (including dropping Node setup from the CI test job and adjusting architecture/CI docs).

Reviewed changes

Copilot reviewed 5 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
yarn.lock	Removes Yarn lockfile (eliminates pinned Node dependency graph).
package.json	Removes Node dependency declaration for @appland/appmap.
Rakefile	Removes Yarn install task and updates spec prerequisites.
README_CI.md	Updates CI documentation wording around repository URL resolution.
ARCHITECTURE.md	Updates description of appmap-js integration to runtime npx usage.
.gitignore	Stops ignoring /.yarn.
.github/workflows/ci.yml	Removes Node setup step from the test job (release job still sets up Node).

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[Copilot]

The test suite exercises code paths that call out to npx/node (e.g., Depends API specs update the AppMap index via AppMap::NodeCLI). With the Node setup step removed, the job now relies on whatever Node/npm happen to be preinstalled on the runner, which can change and can break CI. Re-add actions/setup-node@v4 (and consider cache: npm) for the test job to make the environment deterministic.

Suggested change

	- uses: actions/setup-node@v4
	with:
	node-version: lts/*

[dividedmind]

Non-deterministic is actually good in this case IMO. This reflects more closely how the users will use it and will make it easier to catch any regressions.