docs: enforce deprecation policy - remove browserTarget from user docs

Remove browserTarget from precedence list in BREAKING CHANGE section.
This enforces the established policy: "DO NOT promote deprecated options
in examples or main sections."

browserTarget still works for compatibility (handled in code) but should
not be shown to users. Only contributors need to know about it (CLAUDE.md).

Precedence list now shows only what users should actually use:
1. prerenderTarget (highest priority)
2. buildTarget
3. Default fallback

Author: JohannesHoppe

README.md

@@ -83,10 +83,9 @@ You can also use `prerenderTarget` instead of `buildTarget` for prerendered/SSG
 **Target Resolution Precedence:**
 
 Build target options are resolved in this priority order:
-1. `prerenderTarget` (if specified) — highest priority, overrides all others
-2. `browserTarget` (deprecated, kept for compatibility)
-3. `buildTarget`
-4. Default: `${project}:build:production` if none specified
+1. `prerenderTarget` (if specified) — highest priority
+2. `buildTarget`
+3. Default: `${project}:build:production` if none specified
 
 There is no support for `universalBuildTarget` or `serverTarget` because GitHub Pages only supports static assets and no Server-Side Rendering!