feat(ui): import comprehensive UX system from beads

Import beads' UX design system into gastown:

- Add internal/ui/ package with Ayu theme colors and semantic styling
  - styles.go: AdaptiveColor definitions for light/dark mode
  - terminal.go: TTY detection, NO_COLOR/CLICOLOR support
  - markdown.go: Glamour rendering with agent mode bypass
  - pager.go: Smart paging with GT_PAGER support

- Add colorized help output (internal/cmd/help.go)
  - Group headers in accent color
  - Command names styled for scannability
  - Flag types and defaults muted

- Add gt thanks command (internal/cmd/thanks.go)
  - Contributor display with same logic as bd thanks
  - Styled with Ayu theme colors

- Update gt doctor to match bd doctor UX
  - Category grouping (Core, Infrastructure, Rig, Patrol, etc.)
  - Semantic icons (✓ ⚠ ✖) with Ayu colors
  - Tree connectors for detail lines
  - Summary line with pass/warn/fail counts
  - Warnings section at end with numbered issues

- Migrate existing styles to use ui package
  - internal/style/style.go uses ui.ColorPass etc.
  - internal/tui/feed/styles.go uses ui package colors

Co-Authored-By: SageOx <ox@sageox.ai>

internal/cmd/help.go

@@ -0,0 +1,141 @@
+package cmd
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+
+	"github.com/spf13/cobra"
+	"github.com/steveyegge/gastown/internal/ui"
+)
+
+// colorizedHelpFunc wraps Cobra's default help with semantic coloring.
+// Applies subtle accent color to group headers for visual hierarchy.
+func colorizedHelpFunc(cmd *cobra.Command, args []string) {
+	// build full help output: Long description + Usage
+	var output strings.Builder
+
+	// include Long description first (like Cobra's default help)
+	if cmd.Long != "" {
+		output.WriteString(cmd.Long)
+		output.WriteString("\n\n")
+	} else if cmd.Short != "" {
+		output.WriteString(cmd.Short)
+		output.WriteString("\n\n")
+	}
+
+	// add the usage string which contains commands, flags, etc.
+	output.WriteString(cmd.UsageString())
+
+	// apply semantic coloring
+	result := colorizeHelpOutput(output.String())
+	fmt.Print(result)
+}
+
+// colorizeHelpOutput applies semantic colors to help text
+// - Group headers get accent color for visual hierarchy
+// - Section headers (Examples:, Flags:) get accent color
+// - Command names get subtle styling for scanability
+// - Flag names get bold styling, types get muted
+// - Default values get muted styling
+func colorizeHelpOutput(help string) string {
+	// match group header lines (e.g., "Working With Issues:")
+	// these are standalone lines ending with ":" and followed by commands
+	groupHeaderRE := regexp.MustCompile(`(?m)^([A-Z][A-Za-z &]+:)\s*$`)
+
+	result := groupHeaderRE.ReplaceAllStringFunc(help, func(match string) string {
+		// trim whitespace, colorize, then restore
+		trimmed := strings.TrimSpace(match)
+		return ui.RenderAccent(trimmed)
+	})
+
+	// match section headers in subcommand help (Examples:, Flags:, etc.)
+	sectionHeaderRE := regexp.MustCompile(`(?m)^(Examples|Flags|Usage|Global Flags|Aliases|Available Commands):`)
+	result = sectionHeaderRE.ReplaceAllStringFunc(result, func(match string) string {
+		return ui.RenderAccent(match)
+	})
+
+	// match command lines: "  command   Description text"
+	// commands are indented with 2 spaces, followed by spaces, then description
+	// pattern matches: indent + command-name (with hyphens) + spacing + description
+	cmdLineRE := regexp.MustCompile(`(?m)^(  )([a-z][a-z0-9]*(?:-[a-z0-9]+)*)(\s{2,})(.*)$`)
+
+	result = cmdLineRE.ReplaceAllStringFunc(result, func(match string) string {
+		parts := cmdLineRE.FindStringSubmatch(match)
+		if len(parts) != 5 {
+			return match
+		}
+		indent := parts[1]
+		cmdName := parts[2]
+		spacing := parts[3]
+		description := parts[4]
+
+		// colorize command references in description (e.g., 'comments add')
+		description = colorizeCommandRefs(description)
+
+		// highlight entry point hints (e.g., "(start here)")
+		description = highlightEntryPoints(description)
+
+		// subtle styling on command name for scanability
+		return indent + ui.RenderCommand(cmdName) + spacing + description
+	})
+
+	// match flag lines: "  -f, --file string   Description"
+	// pattern: indent + flags + spacing + optional type + description
+	flagLineRE := regexp.MustCompile(`(?m)^(\s+)(-\w,\s+--[\w-]+|--[\w-]+)(\s+)(string|int|duration|bool)?(\s*.*)$`)
+	result = flagLineRE.ReplaceAllStringFunc(result, func(match string) string {
+		parts := flagLineRE.FindStringSubmatch(match)
+		if len(parts) < 6 {
+			return match
+		}
+		indent := parts[1]
+		flags := parts[2]
+		spacing := parts[3]
+		typeStr := parts[4]
+		desc := parts[5]
+
+		// mute default values in description
+		desc = muteDefaults(desc)
+
+		if typeStr != "" {
+			return indent + ui.RenderCommand(flags) + spacing + ui.RenderMuted(typeStr) + desc
+		}
+		return indent + ui.RenderCommand(flags) + spacing + desc
+	})
+
+	return result
+}
+
+// muteDefaults applies muted styling to default value annotations
+func muteDefaults(text string) string {
+	defaultRE := regexp.MustCompile(`(\(default[^)]*\))`)
+	return defaultRE.ReplaceAllStringFunc(text, func(match string) string {
+		return ui.RenderMuted(match)
+	})
+}
+
+// highlightEntryPoints applies accent styling to entry point hints like "(start here)"
+func highlightEntryPoints(text string) string {
+	entryRE := regexp.MustCompile(`(\(start here\))`)
+	return entryRE.ReplaceAllStringFunc(text, func(match string) string {
+		return ui.RenderAccent(match)
+	})
+}
+
+// colorizeCommandRefs applies command styling to references in text
+// Matches patterns like 'command name' or 'bd command'
+func colorizeCommandRefs(text string) string {
+	// match 'command words' in single quotes (e.g., 'comments add')
+	cmdRefRE := regexp.MustCompile(`'([a-z][a-z0-9 -]+)'`)
+
+	return cmdRefRE.ReplaceAllStringFunc(text, func(match string) string {
+		// extract the command name without quotes
+		inner := match[1 : len(match)-1]
+		return "'" + ui.RenderCommand(inner) + "'"
+	})
+}
+
+func init() {
+	// Set custom help function for colorized output
+	rootCmd.SetHelpFunc(colorizedHelpFunc)
+}