Type the closed enum fields that are still strings as Rust enums #3479

Overview

Several fields that the core schemas declare as closed enums are carried as String in the Rust wire and model types. Give each a Rust enum in nodespace-types, so Rust code names the values instead of comparing strings and the generated TypeScript gets a real union instead of string.

Problem Statement

ADR-086 says closed vocabularies are enums, defined once in nodespace-types. task.status, project.status, priority, query.generated_by, SchemaField.type and the AI-chat turn outcome follow that. These do not:

Consequences:

• Rust compares literals ("processing", "idle", "pty") in the daemon, core behaviours and the AI-chat model, so a typo or a renamed value compiles.
• The generated TypeScript types these fields as string. The frontend keeps a hand-written AiChatProvider union to get the narrowing back, which is the hand-mirroring ADR-086 §8 removes.
• The vocabularies have already drifted: the schema allows a tool_call role, while the frontend's previous hand-written type listed only user | assistant | system.
• An edge field can be declared with a type string outside the field-type vocabulary and is only caught by validation, while a node field's type cannot be constructed wrong.

Proposed Solution

Add one closed enum per vocabulary in nodespace-types (derived serde with the wire spelling, no user-value variant, ts_rs::TS behind the ts feature) and use it in every struct that carries the field:

• AiChatProvider (Native, OpenaiCompat as openai-compat, Pty). The schema's core_values and their labels are built from the enum; AI_CHAT_PROVIDERS stops being a second list.
• AiChatTurnStatus (Idle, Processing).
• AiChatSessionStatus with the values the schema declares when this is implemented (active | archived today; Split ai-chat into an abstract base with ai-chat-native and ai-chat-pty subtypes #3446 renames archived to ended).
• AiChatMessageRole (User, Assistant, System). ADR-088 fixes the role vocabulary to these three and records that the declared tool_call role was never written; drop tool_call from the schema in the same change.
• EdgeField.field_type becomes SchemaFieldType, the enum SchemaField.field_type already uses.

Replace the string comparisons in core, the daemon and the agent with the enums. Regenerate TypeScript and delete the hand-written AiChatProvider union in packages/desktop-app/src/lib/types/ai-chat-node.ts.

For a stored value outside a closed vocabulary (a row written around the service layer), keep each type's existing read behaviour for a malformed field (the conversion falls back to the field's default, as it does for a query's fields) and cover it with a test. Writes are already rejected by schema validation.

Architecture Impact

Implements existing decisions; reverses none.

• decisions/086-core-node-types-defined-once-typed-by-category.md (nodespace-docs) §1 and §4: wire types are defined once in nodespace-types, and closed vocabularies are enums. §8: TypeScript is generated from them.
• decisions/088-ai-chat-subtypes-and-message-nodes.md: role is user | assistant | system, and the declared tool_call message shape was never built.
• components/node-types.md gets the enum names on the AI-chat sheet in the same change. No ADR change.

Acceptance Criteria

• Follows development/node-type-sequence.md (nodespace-docs)
• provider, turn_status, session_status and message role are enums in nodespace-types, used by the wire structs and by core's AI-chat model; no struct carries them as String
• EdgeField.field_type is SchemaFieldType; an edge field with a type outside the vocabulary fails to deserialize (test)
• Each enum's variants equal its schema field's core_values, checked in both directions by a test, as for TaskStatus and ProjectStatus; the provider schema values and labels come from the enum
• No Rust code compares these fields against a string literal ("idle", "processing", "pty", "native", …) outside tests
• The schema's message role no longer lists tool_call
• A stored value outside the vocabulary reads as the field's default without failing the node (test per field)
• bun run gen:types emits a TypeScript union for each enum; the hand-written AiChatProvider union is deleted and its users import the generated type
• bun run test:changed passes; bun run quality:fix clean

Technical Specifications

Reference Files

• packages/nodespace-types/src/ai_chat.rs - AiChatNode (turn_status, session_status, provider), AiChatMessage (role); AiChatTurnOutcome is the closed-enum pattern to copy
• packages/nodespace-types/src/schema.rs - EdgeField.field_type, SchemaFieldType
• packages/nodespace-types/src/query.rs - QueryGeneratedBy, a closed enum with derived serde and a schema default
• packages/nodespace-types/src/project.rs, task.rs - ProjectStatus / TaskStatus and their CORE lists (the extensible-enum pattern; these fields are closed, so no User variant)
• packages/nodespace-types/src/bin/gen_ts.rs - add each new enum to declarations
• packages/core/src/models/ai_chat_node.rs - core's AI-chat model and AI_CHAT_PROVIDERS
• packages/core/src/models/core_schemas.rs - the ai-chat schema's enum fields; test_project_status_variants_match_core_values_bidirectionally is the pin test to mirror
• packages/core/src/behaviors/mod.rs, packages/daemon/src/services/node_service.rs, packages/daemon/src/services/ai_chat_title.rs - string comparisons on turn and session status
• packages/desktop-app/src/lib/types/ai-chat-node.ts - hand-written AiChatProvider; stores/settings.svelte.ts, services/ai-chat-default-model.ts and components/viewers/ai-chat-model-selector.svelte import it

Implementation Details

• Closed enums derive Serialize / Deserialize with #[serde(rename_all = "...")] (kebab-case for provider, lowercase or snake_case for the rest), so ts-rs derives the union from the same attributes and no hand-written serde or #[ts(type)] override is needed.
• The proto messages keep these fields as strings; convert at the daemon and Tauri boundaries, as the project and task status paths do.
• The frontend writes turnStatus: 'processing' to start a turn; after regeneration that literal is checked against the generated union.

Related Issues

• Split ai-chat into an abstract base with ai-chat-native and ai-chat-pty subtypes #3446 (splits ai-chat into subtypes and renames session_status's archived to ended; whichever lands second applies the enums to the other's shape)
• Store AI chat messages as ai-chat-message child nodes with real edges #3448 (moves messages to ai-chat-message nodes; AiChatMessageRole types that node's role)
• Give collection, skill and database-settings typed wire types and updates, and close project and query's gaps #3453 (the flat types' typed wire structs; ProjectStatus landed from it in Type project.status as a ProjectStatus enum with a user-value variant #3476)
• Generate the frontend's wire types from nodespace-types and gate them for drift #3440 (the TypeScript generator)

Non-Goals

• tool.source: Make tool an abstract base with a tool-native subtype and drop source #3450 deletes the field
• The tool-call record fields declared under messages[] (args, status, result_summary, duration_ms): ADR-088 records them as never built, and Store AI chat messages as ai-chat-message child nodes with real edges #3448 replaces the message shape
• Changing any wire spelling or adding values