types: export every public declaration from the package entry point

[roblourens]

Problem

types/index.ts is a hand-maintained allowlist, and it had silently fallen 60 declarations behind the sources. That file is copied verbatim into the published TypeScript client and is its root export, so those declarations weren't merely undocumented — they were unreachable for anyone consuming @microsoft/agent-host-protocol.

Verified against main:

import type { Customization, McpServerState, Icon, SessionMetadata } from './types/index.js';
import { CustomizationType } from './types/index.js';

error TS2305: Module './types/index.js' has no exported member 'Customization'.
error TS2305: Module './types/index.js' has no exported member 'McpServerState'.
error TS2305: Module './types/index.js' has no exported member 'Icon'.
error TS2305: Module './types/index.js' has no exported member 'SessionMetadata'.
error TS2305: Module './types/index.js' has no exported member 'CustomizationType'.

The gaps weren't obscure corners:

• The entire customization subsystem — Customization, CustomizationType, ChildCustomization, and every variant (PluginCustomization, DirectoryCustomization, AgentCustomization, SkillCustomization, PromptCustomization, RuleCustomization, HookCustomization, McpServerCustomization), plus CustomizationLoadState and its four states
• The entire MCP-server state machine — McpServerState, McpServerStatus, McpAuthRequiredReason, and the five state variants
• 13 action types — all four working-directory actions, all four customization actions, all three MCP-server actions, and others
• Icon, ChatInteractivity, InputRequestResponsePart, ToolCallContributor, SessionMetadata, JsonPrimitive, Implementation

Fix

Replace the allowlist with export * from the per-channel shims, so the entry point is complete by construction rather than by maintenance.

Two deliberate exceptions:

• The reducer block stays explicit. The reducers.ts shim also re-exports softAssertNever, an internal exhaustiveness helper that shouldn't be public.
• ChatAction is named explicitly. It's declared twice — by hand in channels-chat/actions.ts and in action-origin.generated.ts — with identical member sets, so export * from both is ambiguous. Naming it preserves the generated declaration the previous list exported. The duplicate declaration itself is left alone; collapsing it is a source change unrelated to this packaging fix, and worth its own look.

Guard

scripts/public-api.test.ts walks the canonical channel modules and asserts every declaration is reachable from the entry point, against a small justified withhold-list. It also asserts the reverse — that nothing on the withhold-list has become reachable — so the list can't quietly go stale.

Verified it actually fails: removing a single export * line makes it fail with the list of newly-unreachable declarations.

Also included

Four stale workingDirectory (singular) references in docs/specification/{chat,session}-channel.md, left over from the 0.7.0 rename to workingDirectories. One of them still described the old "session-level default that chats override" model rather than the current "session-level set that chats restrict to a subset of".

Compatibility

Purely additive — this only adds exports. No wire change, no change to any type, and no other client is affected (the Rust/Kotlin/Swift/Go generators read the channel modules directly and never consulted this barrel).

Verification

• npm test — 381 pass (378 + 3 new), reducer branch coverage at 100%
• npm run generate — no drift
• Built the TypeScript client and type-checked a simulated consumer importing the previously-missing types from the package root: resolves cleanly here, fails on main

_{(Written by Copilot)}