feat: report insufficient quota build failures in chat tools (#24956)

## Summary

When a workspace build fails because the user is over their group quota,
the chat tools currently surface the failure as a bare `"workspace build
failed: insufficient quota"` string with no machine-readable error code
and no visibility into the user's current usage. Agents and the UI
cannot distinguish quota failures from any other Terraform error, so
users see an opaque message and have no clear path to recovery.

This PR tags quota failures with a typed error code at the source and
propagates it through the chat tool layer so callers can react to it
explicitly.

Relates to CODAGT-20

## Changes

**Provisioner runner**

- Add `InsufficientQuotaErrorCode = "INSUFFICIENT_QUOTA"` and set it
explicitly at the `commitQuota` failure site via a new
`failedWorkspaceBuildfCode` helper, so `provisioner_jobs.error_code` is
populated only on the genuine quota path. The substring matcher used for
externally produced sentinels (e.g. `"missing parameter"`, `"required
template variables"`) is intentionally not extended; provider errors
that happen to mention "insufficient quota" stay classified as generic
build failures.

**SDK and API contract**

- Add `JobErrorCodeInsufficientQuota` and a
`JobIsInsufficientQuotaErrorCode` helper to `codersdk`.
- Extend the swagger `enums` tag on `ProvisionerJob.ErrorCode` to
include `INSUFFICIENT_QUOTA`.
- Regenerate `coderd/apidoc`, `docs/reference/api/*`, and
`site/src/api/typesGenerated.ts`.

**chattool create_workspace / start_workspace**

- `waitForBuild` now returns a typed `*workspaceBuildError` carrying
both the message and the `JobErrorCode`, instead of a bare error string.
- New `quotaerror.go` introduces a structured `quotaErrorResult` (with
`error_code`, `title`, `message`, `build_id`, and optional `quota`) and
a best-effort `workspaceQuotaDetails` lookup that wraps owner
authorization internally and fetches `credits_consumed` and `budget`
from the database. Quota lookup failures (including authorization
failures) never block the failure payload.
- On quota-coded build failures, both `create_workspace` and
`start_workspace` now return the structured response (with the recovery
guidance inlined into `message`) instead of the bare `"insufficient
quota"` string. This applies to all three failure paths: post-creation,
an in-progress existing build, and a freshly triggered start build.
Non-quota build failures continue to use the existing
`buildToolResponse` / `newBuildError` path.
- Owner authorization is wrapped only on the call sites that need it
(the `CreateFn` and `StartFn` invocations and the quota-detail lookup),
so idempotent fast paths (already running, already in progress,
existing-workspace early returns) do not pay for an extra RBAC
round-trip or fail when role lookup is transient.

## Out of scope

- No changes to quota math, allowances, or bypass behavior.
- No automatic retries.
- No new quota-inspection tools and no changes to MCP
`coder_create_workspace` (which returns immediately and never observed
the build outcome here).
- No frontend UI changes; those will land in a follow-up PR that
consumes the new `INSUFFICIENT_QUOTA` code.

codersdk/provisionerdaemons.go

@@ -167,6 +167,7 @@ type JobErrorCode string
 
 const (
 	RequiredTemplateVariables JobErrorCode = "REQUIRED_TEMPLATE_VARIABLES"
+	InsufficientQuota         JobErrorCode = "INSUFFICIENT_QUOTA"
 )
 
 // JobIsMissingParameterErrorCode returns whether the error is a missing parameter error.
@@ -181,6 +182,13 @@ func JobIsMissingRequiredTemplateVariableErrorCode(code JobErrorCode) bool {
 	return string(code) == runner.RequiredTemplateVariablesErrorCode
 }
 
+// JobIsInsufficientQuotaErrorCode returns whether the error is an insufficient
+// quota error. This can indicate to consumers that they should explain quota
+// recovery options instead of treating the failure as a generic build error.
+func JobIsInsufficientQuotaErrorCode(code JobErrorCode) bool {
+	return string(code) == runner.InsufficientQuotaErrorCode
+}
+
 // ProvisionerJob describes the job executed by the provisioning daemon.
 type ProvisionerJob struct {
 	ID               uuid.UUID              `json:"id" format:"uuid" table:"id"`
@@ -189,7 +197,7 @@ type ProvisionerJob struct {
 	CompletedAt      *time.Time             `json:"completed_at,omitempty" format:"date-time" table:"completed at"`
 	CanceledAt       *time.Time             `json:"canceled_at,omitempty" format:"date-time" table:"canceled at"`
 	Error            string                 `json:"error,omitempty" table:"error"`
-	ErrorCode        JobErrorCode           `json:"error_code,omitempty" enums:"REQUIRED_TEMPLATE_VARIABLES" table:"error code"`
+	ErrorCode        JobErrorCode           `json:"error_code,omitempty" enums:"REQUIRED_TEMPLATE_VARIABLES,INSUFFICIENT_QUOTA" table:"error code"`
 	Status           ProvisionerJobStatus   `json:"status" enums:"pending,running,succeeded,canceling,canceled,failed" table:"status"`
 	WorkerID         *uuid.UUID             `json:"worker_id,omitempty" format:"uuid" table:"worker id"`
 	WorkerName       string                 `json:"worker_name,omitempty" table:"worker name"`