readme: supported websites, benchmark results, llms.txt for discovery

The README now lists the tuned site shortcuts (Hacker News, Reddit,
DuckDuckGo, Bing) next to the generic engine, and cites the live
benchmark numbers from only-cli/benchmarks. llms.txt gives AI assistants
a one-page summary to index. npm keywords added for search.

The internal build spec moves out of the published repo.

src/act.js

@@ -1,13 +1,12 @@
 /**
  * Actions against a live session: do, fill, submit, read, find, back, next.
- * All of this ships in v0.2 together with session state (see PROMPT.md
- * milestones). The signatures exist now so cli.js wires up once and the
- * command surface stays stable.
+ * All of this ships in v0.2 together with session state. The signatures
+ * exist now so cli.js wires up once and the command surface stays stable.
  */
 
 export class NotImplemented extends Error {
   constructor(command) {
-    super(`'oc ${command}' lands in v0.2, see PROMPT.md milestones. Until then use 'oc open' and 'oc raw'.`);
+    super(`'oc ${command}' lands in v0.2. Until then use 'oc open' and 'oc raw'.`);
   }
 }
 

src/render.js

@@ -28,8 +28,8 @@ export function render(page, { budget = 500 } = {}) {
   let hasInputs = false;
 
   for (const block of collapseRuns(page.blocks)) {
-    // Rule from PROMPT.md: never print the same content twice. Pages often
-    // repeat the title as their first heading.
+    // Never print the same content twice. Pages often repeat the title as
+    // their first heading.
     if (block.type === 'heading' && block.text === page.title) continue;
     const line = formatBlock(block);
     if (!line) continue;
@@ -61,7 +61,7 @@ export function render(page, { budget = 500 } = {}) {
 }
 
 /**
- * The "collapse repeated siblings" rule from PROMPT.md. Long runs of short
+ * Collapse repeated siblings. Long runs of short
  * links are almost always nav chrome (subreddit bars, tag clouds, footers)
  * and would otherwise eat the whole budget before the content starts. Handles
  * are assigned in distill, so the hidden links keep their numbers and the