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/hermes.yaml.tpl

@@ -0,0 +1,47 @@
+name: omarchy
+description: Omarchy system theme
+colors:
+  background: "{{ background }}"
+  ui_text: "{{ foreground }}"
+  ui_primary: "{{ accent }}"
+  ui_accent: "{{ accent }}"
+  ui_border: "{{ muted }}"
+  ui_label: "{{ accent }}"
+  ui_ok: "{{ green }}"
+  ui_warn: "{{ yellow }}"
+  ui_error: "{{ red }}"
+  ui_tool: "{{ cyan }}"
+  ui_thinking: "{{ dark_foreground }}"
+  banner_border: "{{ muted }}"
+  banner_title: "{{ accent }}"
+  banner_accent: "{{ accent }}"
+  banner_dim: "{{ dark_foreground }}"
+  banner_text: "{{ foreground }}"
+  prompt: "{{ bright_foreground }}"
+  input_rule: "{{ muted }}"
+  response_border: "{{ accent }}"
+  shell_dollar: "{{ blue }}"
+  selection_bg: "{{ selection }}"
+  session_label: "{{ accent }}"
+  session_border: "{{ muted }}"
+  status_bar_bg: "{{ dark_background }}"
+  status_bar_text: "{{ foreground }}"
+  status_bar_strong: "{{ accent }}"
+  status_bar_dim: "{{ dark_foreground }}"
+  status_bar_good: "{{ green }}"
+  status_bar_warn: "{{ yellow }}"
+  status_bar_bad: "{{ red }}"
+  status_bar_critical: "{{ bright_red }}"
+  voice_status_bg: "{{ dark_background }}"
+  completion_menu_bg: "{{ lighter_background }}"
+  completion_menu_current_bg: "{{ selection }}"
+  completion_menu_meta_bg: "{{ lighter_background }}"
+  completion_menu_meta_current_bg: "{{ selection }}"
+  diff_added: "{{ mix background green 15% }}"
+  diff_removed: "{{ mix background red 15% }}"
+  diff_added_word: "{{ green }}"
+  diff_removed_word: "{{ red }}"
+  syntax_string: "{{ green }}"
+  syntax_number: "{{ yellow }}"
+  syntax_keyword: "{{ magenta }}"
+  syntax_comment: "{{ muted }}"