v0.3.0

## [0.3.0] — 2026-06-05

Implements AHP 0.3.0.

### Added

- `McpServerCustomization` now exposes the full MCP lifecycle: `enabled`,
  the discriminated `McpServerState` enum
  (`.starting`/`.ready`/`.authRequired`/`.error`/`.stopped`), optional
  `channel` URI for the `mcp://` side-channel, and optional `mcpApp`
  block carrying `AhpMcpUiHostCapabilities` for MCP Apps.
- `McpServerAuthRequiredState` carries `ProtectedResourceMetadata`
  plus `reason` / `requiredScopes` / `description` so the existing
  `authenticate` command can drive per-server auth.
- `Customization.mcpServer` top-level case — hosts MAY surface bare
  MCP servers directly rather than only inside a plugin or directory.
- `SessionMcpServerStateChangedAction` and matching reducer arm —
  narrow upsert of `state` + `channel` on an existing MCP
  server customization by id. Wired through both `Reducers.swift` and
  the protocol-based `NativeReducer.swift`.
- `ClientCapabilities` struct on `InitializeParams.capabilities` with
  first entry `mcpApps`.
- `changeKind` field on `Changeset` (well-known values: `'session'`,
  `'branch'`, `'uncommitted'`, `'turn'`, `'compare-turns'`).
- `status` and `error` fields on `ChangesetOperation` and the
  `changeset/operationStatusChanged` action, tracking the
  `idle → running → error` lifecycle of a changeset operation.
- `AgentCustomization._meta` provider metadata field.
- Optional `changes` field on `SessionSummary` (`ChangesSummary` with optional `additions`, `deletions`, and `files` counts) summarising a session's file-change footprint.


### Changed

- Renamed the `ChangesetSummary` type to `Changeset`. The on-the-wire shape is unchanged.
- Moved the `changesets` catalogue from `SessionSummary` to `SessionState`. The `session/changesetsChanged` action now updates `state.changesets` directly instead of `state.summary.changesets`.

### Removed

- Removed the `additions`, `deletions`, and `files` fields from `ChangesetSummary`. Aggregate counts now live on `SessionSummary.changes`; per-changeset views derive their own totals from `ChangesetState.files`.

### Changed

- `ToolCallBase.toolClientId: String?` replaced by
  `ToolCallBase.contributor: ToolCallContributor?` (enum with
  `.client(ToolCallClientContributor)` and `.mcp(ToolCallMcpContributor)`
  cases). `SessionToolCallStartAction` carries the new `contributor`
  field as well. `Reducers.swift`, `NativeReducer.swift`, and
  `ToolCallStateExtensions.swift` follow the rename.