Add a whitelisted AI tool definition for Wave config updates

[Copilot]

This adds the missing AI tool definition for updating Wave configuration values, without wiring it into tool registration yet. The new tool mirrors the existing config write path (SetConfigCommand / SetBaseConfigValue) while constraining writes to an explicit whitelist instead of exposing the full settings surface.

• New tool definition

  • Adds GetSetConfigToolDefinition() in pkg/aiusechat/tools_setconfig.go
  • Defines a strict set_config tool with:
    • structured config input payload
    • approval requirement before execution
    • callback that applies updates through wconfig.SetBaseConfigValue

• Whitelisted config surface

  • Introduces an explicit allowlist of non-secret config keys
  • Excludes sensitive settings such as AI credentials and other unrestricted config writes
  • Encodes per-key schema and validation rules for:
    • booleans
    • numbers
    • strings
    • constrained enum values
    • null to remove/reset a setting

• Validation behavior

  • Rejects unknown keys up front
  • Rejects values with incompatible types before reaching config write logic
  • Preserves wconfig.SetBaseConfigValue as the final write/typing path

• Focused coverage

  • Adds unit tests for:
    • input parsing
    • whitelist enforcement
    • type/enum validation
    • callback write/remove behavior
    • emitted tool schema

Example tool shape:

func GetSetConfigToolDefinition() uctypes.ToolDefinition {
	return uctypes.ToolDefinition{
		Name:        "set_config",
		ToolLogName: "app:setconfig",
		InputSchema: map[string]any{
			"type": "object",
			"properties": map[string]any{
				"config": map[string]any{
					"type":                 "object",
					"additionalProperties": false,
				},
			},
			"required": []string{"config"},
		},
		ToolAnyCallback: setConfigCallback,
		ToolVerifyInput: verifySetConfigInput,
	}
}

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