feat: localchat, a Go + Templ + HTMX chat app for local Gemma models

Streams replies over SSE from any OpenAI-compatible server (oMLX,
llama.cpp, Ollama, ...). Single binary that can install itself as an
OS service; docker compose bundles llama.cpp + Gemma 4 E2B.

scripts/e2e.py

@@ -0,0 +1,70 @@
+# /// script
+# requires-python = ">=3.11"
+# dependencies = ["playwright"]
+# ///
+"""Browser end-to-end test: loads the UI, sends a message with Enter, waits
+for the streamed reply to finish rendering, and saves screenshots.
+
+    uv run scripts/e2e.py [--url http://127.0.0.1:3000] [--channel msedge]
+"""
+import argparse, sys, time
+from playwright.sync_api import sync_playwright, expect
+
+p = argparse.ArgumentParser()
+p.add_argument("--url", default="http://127.0.0.1:3000")
+p.add_argument("--channel", default="msedge", help="installed browser: chrome, msedge, ...")
+p.add_argument("--out", default="docs")
+p.add_argument("--dark", action="store_true")
+p.add_argument("--prompt", default="Give me 3 short tips for learning Go, as a numbered list. Include one tiny code snippet.")
+args = p.parse_args()
+
+with sync_playwright() as pw:
+    browser = pw.chromium.launch(channel=args.channel, headless=True)
+    page = browser.new_page(viewport={"width": 900, "height": 760},
+                            color_scheme="dark" if args.dark else "light")
+    errors = []
+    page.on("pageerror", lambda e: errors.append(str(e)))
+    page.goto(args.url)
+
+    expect(page.locator("#health .dot.ok")).to_be_visible(timeout=10_000)
+    expect(page.locator(".empty")).to_be_visible()
+
+    box = page.locator("#composer textarea")
+    box.fill(args.prompt)
+    t0 = time.time()
+    box.press("Enter")
+
+    # user bubble shows up and the input clears
+    expect(page.locator(".msg.user")).to_have_count(1)
+    expect(box).to_have_value("")
+    expect(page.locator(".empty")).to_be_hidden()
+
+    # tokens stream in (plain spans) ...
+    page.wait_for_selector(".streaming span", timeout=60_000)
+    first = time.time() - t0
+    # ... then get replaced by rendered Markdown
+    page.wait_for_selector(".msg.assistant .markdown", timeout=180_000)
+    total = time.time() - t0
+    page.wait_for_timeout(300)
+    assert page.locator(".msg.assistant [sse-connect]").count() == 0, "SSE element not cleaned up"
+    if "numbered list" in args.prompt:
+        assert page.locator(".msg.assistant ol li").count() >= 3, "expected a numbered list"
+    if "code" in args.prompt:
+        assert page.locator(".msg.assistant pre code").count() >= 1, "expected a code block"
+    page.screenshot(path=f"{args.out}/screenshot{'-dark' if args.dark else ''}.png")
+
+    # reload: history persists for the session
+    page.reload()
+    expect(page.locator(".msg")).to_have_count(2)
+
+    # new chat clears it
+    page.get_by_role("button", name="New chat").click()
+    expect(page.locator(".msg")).to_have_count(0)
+    expect(page.locator(".empty")).to_be_visible()
+
+    browser.close()
+
+if errors:
+    print("JS errors:", errors)
+    sys.exit(1)
+print(f"OK: first token {first:.1f}s, full reply {total:.1f}s")