feat(durable): code mode listing, tool search, output, models.*, grammar; tool error rule

- structuredOutput is always the tool's own value; a schema tool's error text
  without one becomes a tool_error diagnostic on nested results
- code mode: a schema tool's error result with its value resolves (bash nonzero
  exit), schema-less tools resolve with their text, as in the coding agent
- codemode prompt section with tool declarations by namespace within an inline
  budget; searchTools/describeTool/describeNamespace from the start data
- result layout of the coding agent: header, text markers, console block,
  truncation within max_output_tokens and the tool's output limits, spill and
  image files in a recorded output directory (a rerun overwrites them)
- models.*: catalog globals; classify/generateImages as hidden internal tools
  (nested calls with usage), at most four at once
- Lark grammar of the script source as constrainedSampling

packages/durable/docs/spec.md

@@ -2856,7 +2856,7 @@ interface ToolExecutionApi<TDetails extends JsonValue = JsonValue> extends Docum
 type NestedToolExecutionResult = {
   /** The nested call's tool task. */
   readonly taskId: TaskId;
-  /** A schema tool's validated `structuredOutput`; else, and for an error result without one, its bounded output, collapsed (below). */
+  /** The tool's own value: a schema tool's validated `structuredOutput` (absent on an error result without one, whose text is then a `tool_error` diagnostic); a schema-less tool's bounded output, collapsed (below). */
   readonly structuredOutput?: JsonValue;
   readonly isError: boolean;
   readonly details?: JsonValue;
@@ -2984,19 +2984,20 @@ on an error result, where it may omit it; the Harness validates it after the
 programs get its bounded output, the content the model sees without the
 rendered diagnostics, for a success and for an error alike: one text item as
 its string, one image as its `ImageContent`, no items as `""`, and anything
-else as the content list. A schema tool's error result without
-`structuredOutput` gives programs its bounded output the same way, so they get
-the text of a returned error, for example `"permission denied: /etc"`. A
-thrown error's message is in its `tool_error` diagnostic, not in the output,
-so programs read it there, as they do for any tool. So a
-hook that redacts a tool's output redacts what programs get of a schema-less
-tool and of an error result without structured output. An
+else as the content list. `structuredOutput` is always the tool's own value,
+never text the Harness makes: a schema tool's error result keeps the value it
+returned, and one without gives programs no `structuredOutput`; the text of its
+output becomes a `tool_error` diagnostic of the nested result instead, unless an
+error diagnostic already says what went wrong, so programs get it, for example
+`"permission denied: /etc"`. A thrown error's message is in its `tool_error`
+diagnostic too. So a hook that redacts a schema-less tool's output redacts
+what programs get. An
 error result the Harness writes itself (unavailable, invalid arguments,
 blocked, interrupted, aborted, abandoned, or a scheduler fault) has no
 `structuredOutput`; its diagnostics say what went wrong. A thrown error
 becomes a `tool_error` diagnostic with its message. A nested call whose result breaks this gets an error result
-with an `invalid_structured_output` diagnostic, without the broken value, and
-with its bounded output as `structuredOutput`;
+with an `invalid_structured_output` diagnostic, without the broken value: a
+schema tool's then has no `structuredOutput`, a schema-less tool's its output;
 a model-issued call, whose `structuredOutput` the model never sees, only loses
 it, and the break is reported through `HarnessOptions.onReport`. `structuredOutput` has no size bound;
 keeping it small is the tool's job, as `bash` keeps its retained tail and the
@@ -3557,10 +3558,56 @@ any more (section 2.2).
 `callers: ["model"]`, `replay: "safe"`. Its argument is a script, run with
 pi-codemode's deterministic `sandbox.start()`. The script calls the agent's
 `callable` tools as `tools.<name>(args)`; each call is a nested call with key
-`c<id>`, the VM's own number for the call. A success resolves with the nested
-result's `structuredOutput`; every error rejects, with that `structuredOutput`
-as message when it is a non-empty string (the joined texts of a content list),
-else the error diagnostics' messages, and the value as `error.structuredOutput`.
+`c<id>`, the VM's own number for the call. As in the coding agent, a tool that
+declares `structuredOutputSchema` resolves with its `structuredOutput`, also on an
+error result that carries one (`bash` with a nonzero exit resolves with
+`{ output, exitCode, ... }`, which the script checks), and a schema-less tool
+resolves with its text output, images left out, as its declaration
+(`Promise<string>`) says. Every other error rejects, with the schema-less tool's
+text as message when it is not empty, else the error diagnostics' messages, and
+the value, if any, as `error.structuredOutput`. Which tools declare a schema is
+recorded in the start data, so a resumed script maps results as it began.
+
+The tool's description is fixed: the script environment and its globals. The
+extension's `codemode` prompt section lists the agent's `callable` tools as
+TypeScript declarations, grouped by `namespaces` (a tool belongs to the one with
+the longest matching name prefix), within an inline budget of 3000 estimated
+tokens: every namespace places its cheapest tool before any places a second,
+and what does not fit is said so and found with `searchTools()`. Scripts find
+tools with `ALL_TOOLS`, `searchTools(query, { limit?, namespace? })` (BM25),
+`describeTool(name)`, and `describeNamespace(name)`, answered from the start
+data and journaled like other globals. The result's content is a
+`Script completed`/`Script failed` header with the wall time since
+`startedAt`, the text items (`==> text N/M <==` when there are several), the
+`console` lines in one `<console_output>` block, the returned value, and on
+failure the error with the calls already made. Text past `max_output_tokens`
+(default 10000) keeps its start and end, the complete text written to a file
+(`details.fullOutputPath`); images are saved to files, their paths next to them.
+The Harness cuts a result past the tool's `outputLimits` (4 MiB, 100,000 lines)
+without such a file, so the text is also cut when it exceeds 1 Mi characters or
+the line limit, whatever `max_output_tokens` says. The files go to a temp
+directory of the environment that the run creates once and records in its run
+document (`outputDir`) before writing to it, under fixed names (`output.txt`,
+`image-<n>.<ext>`): a rerun after a crash overwrites them instead of adding new
+ones.
+
+With `models` (default on), scripts get the model catalog
+(`models.getModelsOfType`, `getAvailableOfType`, `getModelOfType`; journaled
+globals, configured `headers` removed) and `models.classify()` and
+`models.generateImages()`. Those two are paid effects, so each runs as an
+internal tool of the extension, `pi.codemode.models.classify` and
+`pi.codemode.models.generateImages` (`callers: ["tools"]`): the code mode tool
+turns the script's call of the global into a nested call of the tool, which then
+has its own task, live row, abort, usage accounting, and replay policy. Tools
+named `pi.codemode.*` are recorded in the start data as `hidden`: never in the
+section, `tools`, `ALL_TOOLS`, or tool search. They declare a schema, so like any
+such tool they resolve with the model's result whatever its `stopReason`, which
+the script checks; their rows show a failed one as an error. At most four such
+calls of one script run at once, and a call waiting for a slot when the script
+has ended is not started. A script that
+received generated images and showed none gets a note in its result. The tool's
+declaration carries the Lark grammar of the script source as
+`constrainedSampling`, which pi-ai applies for models that support it.
 
 The result's \`details\` list the script's tool calls in call order
 (\`CodemodeToolDetails\`: id, name, cut arguments, status \`ok\`/\`error\`/