Skip Node/TS subtrees and gitignored files in workspace validate

[zekelinAlex]

Closes #74.

workspace validate was running Dataverse XSD/JSON validation against
every file in the workspace, which produced a wall of false errors in
any repo with a PCF control or a TypeScript subproject. node_modules
contents, tsconfig.json, package-lock.json, eslintrc, you name it.
None of those are Dataverse metadata, but the validator didn't know.

Now the command filters before reporting:

• well-known throwaway dirs are skipped (node_modules, bin, obj, out, dist, .git, .vs, .idea, .vscode, .cache, .nuget, coverage)
• the workspace .gitignore is honored (basic semantics: directory-only, anchored, ** wildcards; negations are no-ops)
• any directory containing a package.json marks the whole subtree as a Node/TS project and gets skipped, which covers tsconfig.json, package.json itself, lockfiles, lint configs without a hand-curated allowlist

Two escape hatches: --no-ignore turns everything off (original
behaviour), --no-gitignore keeps defaults + node-project detection
but ignores .gitignore.