chore(deps): move the whole Angular train to 21.2.23

[adamjohnwright]

Replaces dependabot's #161, which cannot be merged as it stands.

Why #161 cannot be taken

It moves eleven Angular packages from 21.2.20 to 21.2.22 and leaves
@angular/platform-browser-dynamic and @angular/compiler-cli behind. Angular's
packages peer-depend on one another at exact versions, so the result does not
resolve:

Conflicting peer dependency: @angular/core@21.2.23
  peer @angular/core@"21.2.23" from @angular/platform-browser-dynamic@21.2.23

Its checks pass only because CI installs with --legacy-peer-deps. #215 removes
that flag; after it, #161 fails honestly rather than passing on a tree that only
installs when npm is told not to look.

What this does instead

The train moves together — core, common, compiler, compiler-cli, forms, router,
elements, localize, platform-browser, platform-browser-dynamic to 21.2.23, and
the CLI train (cli, ssr, build-angular) to its own.

The diff is large, and deliberately so

package-lock.json is regenerated from scratch, not hand-resolved: +7334
−8144. A partially-merged lock is what produced the conflict in the first place,
and resolving one by hand is how you get a tree that installs but is not what
anyone described.

The thing to check is not the diff's size but whether it resolves without help:

npm ci --dry-run --no-audit --no-fund   → added N packages, no ERESOLVE

Verified, not assumed

• npm ci strictly, with no --legacy-peer-deps
• 242 unit tests, types, lint 652, dead code 145, format, full build
• 49 e2e cases against the resulting build: interactors, the confidence
  threshold, the custom-resource dialog, the homepage, content pages, the back
  button

The diagram is what an Angular bump would break, so the diagram is what was
exercised.

Closes #161 once merged.

🤖 Generated with Claude Code