feat(ui): 15-point UX overhaul — affordances, feedback, and navigation

Address friction points identified in a full interface audit:
- Re-add status badge to dashboard tiles so run state is visible at a glance
- Add active nav indicator and SSE connection health monitor (live/stale)
- Show manual registration form by default instead of hiding behind <details>
- Add copy-to-clipboard buttons on SSH hold command and quick-register one-liner
- Replace tooltip-only profile descriptions with inline visible text
- Clarify non-destructive toggle with explicit stage impact description
- Replace disabled "Start vetting" button with actionable offline guidance
- Swap browser confirm() dialogs for styled inline confirmations
- Add colored badge to spec diffs summary visible when collapsed
- Add distinct "cancelled" mood for cancelled runs (vs idle)
- Add match count to log search and aria-label for accessibility
- Add styled 404 page rendered inside the app shell

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/web/templates/not_found_templ.go

@@ -0,0 +1,58 @@
+// Code generated by templ - DO NOT EDIT.
+
+// templ: version: v0.3.1001
+package templates
+
+//lint:file-ignore SA4006 This context is only used if a nested component is present.
+
+import "github.com/a-h/templ"
+import templruntime "github.com/a-h/templ/runtime"
+
+func NotFound() templ.Component {
+	return templruntime.GeneratedTemplate(func(templ_7745c5c3_Input templruntime.GeneratedComponentInput) (templ_7745c5c3_Err error) {
+		templ_7745c5c3_W, ctx := templ_7745c5c3_Input.Writer, templ_7745c5c3_Input.Context
+		if templ_7745c5c3_CtxErr := ctx.Err(); templ_7745c5c3_CtxErr != nil {
+			return templ_7745c5c3_CtxErr
+		}
+		templ_7745c5c3_Buffer, templ_7745c5c3_IsBuffer := templruntime.GetBuffer(templ_7745c5c3_W)
+		if !templ_7745c5c3_IsBuffer {
+			defer func() {
+				templ_7745c5c3_BufErr := templruntime.ReleaseBuffer(templ_7745c5c3_Buffer)
+				if templ_7745c5c3_Err == nil {
+					templ_7745c5c3_Err = templ_7745c5c3_BufErr
+				}
+			}()
+		}
+		ctx = templ.InitializeContext(ctx)
+		templ_7745c5c3_Var1 := templ.GetChildren(ctx)
+		if templ_7745c5c3_Var1 == nil {
+			templ_7745c5c3_Var1 = templ.NopComponent
+		}
+		ctx = templ.ClearChildren(ctx)
+		templ_7745c5c3_Var2 := templruntime.GeneratedTemplate(func(templ_7745c5c3_Input templruntime.GeneratedComponentInput) (templ_7745c5c3_Err error) {
+			templ_7745c5c3_W, ctx := templ_7745c5c3_Input.Writer, templ_7745c5c3_Input.Context
+			templ_7745c5c3_Buffer, templ_7745c5c3_IsBuffer := templruntime.GetBuffer(templ_7745c5c3_W)
+			if !templ_7745c5c3_IsBuffer {
+				defer func() {
+					templ_7745c5c3_BufErr := templruntime.ReleaseBuffer(templ_7745c5c3_Buffer)
+					if templ_7745c5c3_Err == nil {
+						templ_7745c5c3_Err = templ_7745c5c3_BufErr
+					}
+				}()
+			}
+			ctx = templ.InitializeContext(ctx)
+			templ_7745c5c3_Err = templruntime.WriteString(templ_7745c5c3_Buffer, 1, "<section class=\"not-found\"><h1>Page not found</h1><p>The host or run you're looking for doesn't exist or has been deleted.</p><a class=\"button\" href=\"/\">Back to dashboard</a></section>")
+			if templ_7745c5c3_Err != nil {
+				return templ_7745c5c3_Err
+			}
+			return nil
+		})
+		templ_7745c5c3_Err = Layout("Not found").Render(templ.WithChildren(ctx, templ_7745c5c3_Var2), templ_7745c5c3_Buffer)
+		if templ_7745c5c3_Err != nil {
+			return templ_7745c5c3_Err
+		}
+		return nil
+	})
+}
+
+var _ = templruntime.GeneratedTemplate