fix: linker compiles hostBindings/hostVars for directives and emits signals flag (#83)

The linker's `link_directive` was only generating `hostAttrs` for static
host attributes, but was missing compilation of dynamic host bindings
(`hostVars` and `hostBindings`). This caused directives like RouterLink
to lose their host property bindings (href, target) and event listeners
(click) at runtime, making them non-functional.

Also adds `signals: true` emission for both directives and components
when the partial declaration has `isSignal: true`, aligning with the
Angular TS compiler's `baseDirectiveFields` output.

- Close #72

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: Brooooooklyn