feat(docs): standalone docs site chrome + category/subcategory navigation

Docs pages no longer embed the app Header (whose hx-post login form silently
degraded to a native GET, leaking credentials into the URL — this page never
loaded htmx). New docs-owned topbar: search, theme picker, Open App; anonymous
visitors get a plain /login link. Optional-auth middleware (hand-rolled —
echojwt's ErrorHandler return ends the chain, producing empty 200s) populates
the user for signed-in visitors.

Navigation rebuilt from the docs directory tree: 6 sections, subcategory
groups, server-rendered expansion and active states. Search results are a
templ partial (/docs/search/partial); code highlighting is server-side chroma
(previously dead hljs CSS); prose is theme-aware via typography DEFAULT vars
(prose-invert painted unreadable text under light themes). /docs renders the
index directly; standalone 404 without the tailwind CDN.

Tests: navigation routing/expansion (internal/docs), render pins asserting no
login form/password field/app sidebar ever return on docs pages.
lint-rendering: exempt *.test.ts fixtures (jsdom DOM building); docs.ts
baseline 5 -> 1.

templates/docs_render_test.go

@@ -0,0 +1,146 @@
+package templates
+
+import (
+	"context"
+	"strings"
+	"testing"
+)
+
+// The docs layout is a standalone documentation site: it must NOT embed the
+// app chrome (its sidebar assumed a signed-in user) and must never contain a
+// login form — the old layout posted credentials via htmx that was never
+// loaded on this page, degrading to a native GET that put the username and
+// password into the URL. These render tests pin that fix.
+func TestDocsLayoutRendersStandalone(t *testing.T) {
+	nav := Navigation{
+		Sections: []NavSection{
+			{
+				Title: "Getting Started",
+				Icon:  "book-open",
+				Items: []NavItem{{Title: "Overview", URL: "/docs"}},
+			},
+			{
+				Title:     "User Guide",
+				Icon:      "book",
+				Collapsed: true,
+				Items:     []NavItem{{Title: "Dashboard", URL: "/docs/user/dashboard"}},
+				Groups: []NavGroup{
+					{
+						Title:     "Devices",
+						Items:     []NavItem{{Title: "Kobo Setup", URL: "/docs/user/devices/kobo-setup"}},
+						Collapsed: true,
+					},
+				},
+			},
+		},
+	}
+	doc := Document{
+		Title:   "Test Doc",
+		Content: "<p>Hello docs</p>",
+		TOC:     []TOCItem{{Level: 2, Title: "Section", Anchor: "section"}},
+		Breadcrumb: []BreadcrumbItem{
+			{Title: "Docs", URL: "/docs"},
+			{Title: "User Guide"},
+		},
+		SourceFile: "user/test.md",
+	}
+
+	var b strings.Builder
+	if err := DocsLayout(nav, doc, User{Theme: "tokyo-night"}, "/docs/user/test").Render(context.Background(), &b); err != nil {
+		t.Fatalf("DocsLayout: %v", err)
+	}
+	out := b.String()
+
+	for _, banned := range []string{
+		"app-sidebar",               // app chrome
+		`hx-post="/api/auth/login"`, // no inline login form (the URL-leak bug)
+		`name="password"`,           // credentials never render on docs pages
+		"prose-invert",              // theme-aware prose, not hardcoded dark
+		"highlight-dark.min.css",    // highlighting is server-side now
+		"cdn.tailwindcss.com",       // no CDN dependencies
+		"lunr",                      // dead client-side search is gone
+	} {
+		if strings.Contains(out, banned) {
+			t.Errorf("docs layout must not contain %q", banned)
+		}
+	}
+
+	for _, want := range []string{
+		`href="/docs"`,           // sidebar + logo links
+		`data-collapsed="true"`,  // collapsed section state
+		`data-collapsed="false"`, // expanded section state
+		"Open App",               // topbar action
+		"theme-select",           // theme picker
+		"docs-search-results",    // search dropdown target
+		"Hello docs",             // content rendered
+		"page-docs",
+	} {
+		if !strings.Contains(out, want) {
+			t.Errorf("docs layout missing %q", want)
+		}
+	}
+
+	// Anonymous visitor: a sign-in LINK, never a form.
+	b.Reset()
+	if err := DocsLayout(nav, doc, User{Theme: "tokyo-night"}, "/docs/user/test").Render(context.Background(), &b); err != nil {
+		t.Fatalf("DocsLayout anonymous: %v", err)
+	}
+	if !strings.Contains(b.String(), `href="/login"`) {
+		t.Error("anonymous docs layout should link to /login")
+	}
+}
+
+func TestDocsTopbarSignedIn(t *testing.T) {
+	var b strings.Builder
+	if err := DocsTopbar(User{ID: "u1", Username: "reader", Theme: "tokyo-night"}).Render(context.Background(), &b); err != nil {
+		t.Fatalf("DocsTopbar: %v", err)
+	}
+	out := b.String()
+	if strings.Contains(out, `href="/login"`) {
+		t.Error("signed-in topbar must not offer /login")
+	}
+	if !strings.Contains(out, "reader") {
+		t.Error("signed-in topbar should surface the username")
+	}
+}
+
+func TestDocsSearchResultsPartial(t *testing.T) {
+	var b strings.Builder
+	results := []SearchResultItem{
+		{Title: "Kobo Setup", Category: "User Guide", URL: "/docs/user/devices/kobo-setup"},
+	}
+	if err := DocsSearchResults(results).Render(context.Background(), &b); err != nil {
+		t.Fatalf("DocsSearchResults: %v", err)
+	}
+	out := b.String()
+	for _, want := range []string{"Kobo Setup", "User Guide", `/docs/user/devices/kobo-setup`} {
+		if !strings.Contains(out, want) {
+			t.Errorf("search results missing %q", want)
+		}
+	}
+
+	// Empty state renders, not blank markup.
+	b.Reset()
+	if err := DocsSearchResults(nil).Render(context.Background(), &b); err != nil {
+		t.Fatalf("DocsSearchResults empty: %v", err)
+	}
+	if !strings.Contains(b.String(), "No matching pages.") {
+		t.Error("search results empty state missing")
+	}
+}
+
+func TestDocsNotFoundRenders(t *testing.T) {
+	var b strings.Builder
+	if err := DocsNotFound("Document Not Found", "no such page").Render(context.Background(), &b); err != nil {
+		t.Fatalf("DocsNotFound: %v", err)
+	}
+	out := b.String()
+	for _, want := range []string{"Document Not Found", "no such page", `href="/docs"`} {
+		if !strings.Contains(out, want) {
+			t.Errorf("404 page missing %q", want)
+		}
+	}
+	if strings.Contains(out, "cdn.tailwindcss.com") {
+		t.Error("404 page must not pull the tailwind CDN")
+	}
+}