feat: add model_intent option to MCP server configs (#23717)

Add a per-MCP-server `model_intent` toggle that wraps tool schemas with
a
`model_intent` field, requiring the LLM to provide a human-readable
description of each tool call's purpose. The intent string is shown as a
status label in the UI instead of opaque tool names, and is
transparently
stripped before the call reaches the remote MCP server.

Built-in tools have rich specialized renderers (terminal blocks, file
diffs,
etc.) and don't need this. MCP tools hit `GenericToolRenderer` which
only
shows raw tool names and JSON — that's where model_intent adds value.

The model learns what to provide via the JSON Schema `description` on
the
`model_intent` property itself — no system prompt changes needed.

<details>
<summary>Implementation details</summary>

### Architecture

Inspired by the `withModelIntent()` pattern from `coder/blink`, adapted
for
Go + React. The wrapping is entirely in the `mcpclient` layer — tool
implementations never see `model_intent`.

**Schema wrapping** (`mcpToolWrapper.Info()`): When enabled, wraps the
original tool parameters under a `properties` key and adds a
`model_intent`
string field with a rich description that teaches the model inline.

**Input unwrapping** (`mcpToolWrapper.Run()`): Strips `model_intent` and
unwraps `properties` before forwarding to the remote MCP server. Handles
three input shapes models may produce:
1. `{ model_intent, properties: {...} }` — correct format
2. `{ model_intent, key: val, ... }` — flat, no wrapper
3. Malformed — falls through gracefully

**Frontend extraction**: `streamState.ts` extracts `model_intent` from
incrementally parsed streaming JSON. `messageParsing.ts` extracts it
from
persisted tool call args.

**UI rendering**: `GenericToolRenderer` shows the capitalized intent
string
as the primary label when available, falling back to the raw tool name.

### Changes
- Database: `model_intent` boolean column on `mcp_server_configs`
- SDK: `ModelIntent` field on config/create/update types
- API: pass-through in create/update handlers + converter
- mcpclient: schema wrapping in `Info()`, input unwrapping in `Run()`
- Frontend: extraction from streaming + persisted args
- UI: intent label in `GenericToolRenderer`, toggle in admin panel
- Tests: 6 new tests (schema wrapping, unwrapping, passthrough,
fallback)

### Decision log
- **Option lives on MCPServerConfig, not model config**: Built-in tools
  already have rich renderers; only MCP tools benefit from model_intent.
- **No system prompt changes**: The JSON Schema `description` on the
  `model_intent` property teaches the model inline.
- **Pointer bool on update request**: Follows existing pattern (`*bool`)
  so PATCH requests don't reset the value when omitted.

</details>

coderd/database/models.go

@@ -4488,6 +4488,7 @@ type MCPServerConfig struct {
 	UpdatedBy               uuid.NullUUID  `db:"updated_by" json:"updated_by"`
 	CreatedAt               time.Time      `db:"created_at" json:"created_at"`
 	UpdatedAt               time.Time      `db:"updated_at" json:"updated_at"`
+	ModelIntent             bool           `db:"model_intent" json:"model_intent"`
 }
 
 type MCPServerUserToken struct {