agent: drop dated prompt patterns

- Synthesis prompt: drop the one-word/one-phrase answer clamp (a
  benchmark format applied to every budget-exhausted REPL turn) and the
  no-more-tools line the request already enforces; keep the
  report-don't-confabulate rule.
- Driver guidance: drop the HN/Reddit source heuristic, which also
  reached every MCP client.
- Save prompt: state the comment rule once instead of repeating it in
  the output-format line.
- goto: describe when it returns, what it returns, and when a url-taking
  read is the better call.

src/agent/Agent.zig

@@ -118,16 +118,12 @@ fn savePrompt(revision: bool) []const u8 {
 
 const synthesis_prompt =
     \\You have used your tool budget or cannot finish the exploration.
-    \\Give your best final answer NOW based ONLY on what you actually observed
-    \\via tool calls in this conversation. Do NOT fall back to prior knowledge —
-    \\if your snapshots show only cookie banners, 403/access-denied pages,
-    \\blocked search results, or empty bodies, say that explicitly
-    \\(e.g. "the page was blocked by a cookie wall and I could not extract X").
-    \\Do not invent details that are not visible in the tool outputs above.
-    \\Do not call any more tools.
-    \\Respond with ONLY the answer — one word, one number, one short phrase,
-    \\or a brief honest explanation of why the page could not be read.
-    \\No prefix, no markdown.
+    \\Give your best final answer using only what the tool outputs above
+    \\show, not prior knowledge. If they show only cookie banners,
+    \\403/access-denied pages, blocked search results, or empty bodies, say
+    \\so plainly (e.g. "the page was blocked by a cookie wall and I could not
+    \\extract X") rather than filling the gap. Answer at the length the
+    \\question needs.
 ;
 
 allocator: std.mem.Allocator,

src/browser/tools.zig

@@ -106,9 +106,7 @@ pub const driver_guidance =
     \\- Triage from `search` snippets before opening links; open only the few
     \\  most promising. Don't re-run a search you already ran, and skip
     \\  near-duplicate sources that repeat the same announcement verbatim.
-    \\- Stop once the gathered material answers the question. For opinion or
-    \\  discussion questions, a couple of high-signal threads (e.g. Hacker
-    \\  News, Reddit) usually beat scraping a dozen news sites.
+    \\- Stop once the gathered material answers the question.
     \\
     \\Selector rules:
     \\- NEVER pass backendNodeId to click/fill/hover/selectOption/setChecked.
@@ -179,9 +177,8 @@ pub const save_synthesis_prompt =
     \\list, fan out to detail pages, aggregate, return) stating what that block
     \\accomplishes toward the goal — NOT restating the API call. One comment per
     \\step, not per line; skip self-evident lines.
-    \\Output ONLY JavaScript source — no markdown fences and no prose outside the
-    \\code, but DO annotate the script with the `//` intent comments described
-    \\above.
+    \\Output the JavaScript source alone, with no markdown fences or prose
+    \\around it.
 ;
 
 /// Script-language rules for consumers that never see the full
@@ -345,7 +342,7 @@ pub const Tool = enum {
     pub fn definition(self: Tool) Definition {
         return switch (self) {
             .goto => .{
-                .description = "Navigate to a specified URL and load the page in memory so it can be reused later for info extraction.",
+                .description = "Navigate the current page to a URL. Returns a short status once `waitUntil` fires (default `load`), or a timeout notice; content rendered by post-load JavaScript may not be there yet (see `waitForState`). The page stays loaded for later reads and actions. To navigate and read in one call, pass `url` to `markdown`, `tree` or `html` instead; use `goto` when the next step is an action or `extract`.",
                 .summary = "Open a URL and keep the page in memory",
                 .input_schema = minify(
                     \\{