feat(themes): add color derivation and themed app templates

Add script/omarchy-theme-color and expand omarchy-theme-set-templates to
derive a full palette from each theme's colors.toml, then render new
themed templates (shell, pi, vscode theme, gum, neovim, claude, hermes,
t3code) from it.

Adds backgrounds and palette updates for existing themes plus new themes
(last-horizon, lupine, solitude, tidewater-*, miasma, ...).

default/themed/claude.json.tpl

@@ -0,0 +1,43 @@
+{
+  "name": "Omarchy",
+  "base": "{{ theme_type }}",
+  "overrides": {
+    "claude": "{{ accent }}",
+    "claudeShimmer": "{{ mix accent foreground 35% }}",
+    "text": "{{ foreground }}",
+    "inverseText": "{{ background }}",
+    "inactive": "{{ mix foreground background 40% }}",
+    "inactiveShimmer": "{{ mix foreground background 25% }}",
+    "subtle": "{{ muted }}",
+    "suggestion": "{{ cyan }}",
+    "permission": "{{ blue }}",
+    "permissionShimmer": "{{ mix blue foreground 35% }}",
+    "remember": "{{ yellow }}",
+    "success": "{{ green }}",
+    "error": "{{ red }}",
+    "warning": "{{ yellow }}",
+    "warningShimmer": "{{ mix yellow foreground 35% }}",
+    "merged": "{{ magenta }}",
+    "promptBorder": "{{ accent }}",
+    "promptBorderShimmer": "{{ mix accent foreground 35% }}",
+    "planMode": "{{ cyan }}",
+    "autoAccept": "{{ yellow }}",
+    "bashBorder": "{{ bright_yellow }}",
+    "ide": "{{ bright_cyan }}",
+    "diffAdded": "{{ mix background green 15% }}",
+    "diffRemoved": "{{ mix background red 15% }}",
+    "diffAddedDimmed": "{{ mix background green 8% }}",
+    "diffRemovedDimmed": "{{ mix background red 8% }}",
+    "diffAddedWord": "{{ mix background green 32% }}",
+    "diffRemovedWord": "{{ mix background red 32% }}",
+    "userMessageBackground": "{{ mix background foreground 6% }}",
+    "userMessageBackgroundHover": "{{ mix background foreground 10% }}",
+    "bashMessageBackgroundColor": "{{ mix background foreground 6% }}",
+    "memoryBackgroundColor": "{{ mix background foreground 6% }}",
+    "selectionBg": "{{ selection_background }}",
+    "rate_limit_fill": "{{ accent }}",
+    "rate_limit_empty": "{{ mix background foreground 20% }}",
+    "briefLabelYou": "{{ yellow }}",
+    "briefLabelClaude": "{{ accent }}"
+  }
+}