Upgrade to Angular 21.2.9

[norman-abramovitz]

Summary

Upgrade from the current Angular 21 baseline to Angular 21.2.9.

Motivation

Keep dependencies current and pick up bug fixes and performance improvements in the 21.x patch series.

Angular 21.2 also introduces experimental signal-based forms and new components. These are likely not immediately usable in Stratos, but worth reviewing for ideas — particularly signal forms as a potential future direction given our existing signal-based validity propagation work.

Acceptance Criteria

• All Angular packages updated to 21.2.9
• Gate check passes (lint + vitest)
• App starts and smoke-tests clean on adepttech

Notes

• Review Angular 21.2 release notes for signal forms API and new components during upgrade
• Flag anything relevant to Stratos form patterns as follow-up candidates