fix(coding-agent): pass host keybinding hints to extension renderers (#11630)

Fixes #4748.

## Problem

Extensions that import `keyText`/`keyHint` from
`@earendil-works/pi-coding-agent` can resolve their own copy of the
package (their own `node_modules`, or the bundled `cli.js` vs
`dist/index.js`). That copy's keybindings are never set by the host, so
it falls back to a manager with only `tui.*` bindings, and
`keyHint("app.tools.expand", "to expand")` renders as ` to expand`.

## Change

The host passes its own `keyText` and `keyHint` to extension renderers,
the same way it passes `theme`:

- `ToolRenderContext` (`renderCall`/`renderResult` context):
`context.keyHint(...)`
- `MessageRenderOptions` and `EntryRenderOptions`:
`options.keyHint(...)`

All three extend a new exported `KeybindingHints` interface. The docs
and the `debug-provider` example now use the injected functions and warn
against importing them in renderers.

Not done:

- Moving the `pi-tui` keybindings singleton to `globalThis`. Per the
discussion in #7011, extension-facing state should be host-owned and
passed through the extension API instead of shared through process-wide
module state.
- `ctx.ui.keyText`/`keyHint`. No reported case needs them outside
renderers, RPC and print modes never install app keybindings, and adding
them to `ExtensionUIContext` would break SDK hosts that implement it.

## Tests

- `test/extension-keybinding-hints.test.ts`: tool, message, and entry
renderers format a user-overridden `app.tools.expand` binding.
- `npm run check` passes.

packages/coding-agent/docs/extensions.md

@@ -2520,6 +2520,7 @@ pi.registerTool({
 - `toolCallId`, `cwd`, `executionStarted`, `argsComplete`, `isPartial`, `expanded`, `showImages`, `isError`
 - `durationMs` - how long execution took, from the final result; `undefined` while running
 - `outputPad` - horizontal padding from the `outputPad` setting; renderers with `renderShell: "self"` apply it themselves
+- `keyText()`, `keyHint()` - format the user's configured keybindings, see [Keybinding Hints](#keybinding-hints)
 
 Use `context.state` for cross-slot shared state. Keep slot-local caches on the returned component instance when you want to reuse and mutate the same component across renders.
 
@@ -2570,24 +2571,24 @@ If a slot intentionally has no visible content, return an empty `Component` such
 
 #### Keybinding Hints
 
-Use `keyHint()` to display keybinding hints that respect the active keybinding configuration:
+Use `keyHint()` and `keyText()` from the render context to display keybinding hints that respect the user's keybinding configuration:
 
 ```typescript
-import { keyHint } from "@earendil-works/pi-coding-agent";
-
 renderResult(result, { expanded }, theme, context) {
   let text = theme.fg("success", "✓ Done");
   if (!expanded) {
-    text += ` (${keyHint("app.tools.expand", "to expand")})`;
+    text += ` (${context.keyHint("app.tools.expand", "to expand")})`;
   }
   return new Text(text, 0, 0);
 }
 ```
 
-Available functions:
-- `keyHint(keybinding, description)` - Formats a configured keybinding id such as `"app.tools.expand"` or `"tui.select.confirm"`
-- `keyText(keybinding)` - Returns the raw configured key text for a keybinding id
-- `rawKeyHint(key, description)` - Format a raw key string
+The same functions are available as `options.keyHint()`/`options.keyText()` in message and entry renderers:
+
+- `keyHint(keybinding, description)` - Formats a configured keybinding id such as `"app.tools.expand"` or `"tui.select.confirm"`, followed by the description
+- `keyText(keybinding)` - Returns the raw configured key text for a keybinding id, or `""` if the id has no keys
+
+In renderers, use these instead of importing `keyHint()` or `keyText()` from `@earendil-works/pi-coding-agent`. An extension can resolve its own copy of the package, for example from its own `node_modules`, and that copy does not see pi's configured keybindings: `app.*` ids then format as `""`. `rawKeyHint(key, description)` formats a literal key string and is safe to import.
 
 Use namespaced keybinding ids:
 - Coding-agent ids use the `app.*` namespace, for example `app.tools.expand`, `app.editor.external`, `app.session.rename`
@@ -3144,6 +3145,8 @@ pi.registerMessageRenderer("my-extension", (message, options, theme) => {
 
   if (expanded && message.details) {
     text += "\n" + theme.fg("dim", JSON.stringify(message.details, null, 2));
+  } else if (message.details) {
+    text += ` (${options.keyHint("app.tools.expand", "to expand")})`;
   }
 
   return new Text(text, outputPad, 0);