refactor(infinity-protocol)!: session_id becomes root_thread_id; add ThreadRef

[MingweiSamuel]

Stage 3 of the string-ID to typed-ID migration (#108), implementing the
decision that a session IS its root thread. This is the one deliberate
wire-format break of the migration: JSON field names change; values are
unchanged (ThreadRef serializes as the historical composite string).
Verified end-to-end: full test suite + Playwright web e2e (7/7) against
the live daemon.

• infinity-protocol: session_id renamed to root_thread_id across
  ClientMessage/DaemonMessage (new_session_id to new_root_thread_id;
  SwitchModel's mislabeled session_id is now honestly thread_id). New
  ThreadRef { remote: Option<RemoteName>, id: ThreadId } replaces the
  ad-hoc "remote/uuid" string encoding: Display/FromStr/serde use the
  composite form, .prefixed()/.strip() replace split_once logic; Ord
  derives (local-before-remote, then id). New RemoteName kind; typed
  location/to/on fields, SessionInfo.remote, RemoteInfo.name,
  SubthreadInfo, and sessions maps keyed by ThreadRef. Client-facing
  fields are ThreadRef; daemon-to-daemon variants (Emigrate family) are
  plain ThreadId
• infinity-daemon: IdSource::generate() -> ThreadId; client_handler's
  is_remote_session/strip_id string surgery replaced by ThreadRef
  operations; remote.rs session maps and control workers typed
  (RemoteConfig.name: RemoteName, remotes.json unchanged); migrate.rs
  orchestration fully typed (composite-string juggling eliminated)
• rap-client: ToolsetLoader::load_toolsets and
  RapNotifier::request_migration take &ThreadId; rap-bridge connect too
• infinity-agent-cli (sub-agent): terminal state keyed by ThreadRef,
  session picker/daemon client typed, ACP boundary documented (ACP-side
  ids stay String; acp-sessions.json format unchanged); zero terminal
  snapshot changes
• infinity-slack-bot + TS (sub-agent): SessionStore/DaemonCommand/client
  typed with ThreadRef (persisted JSON unchanged); infinity-ui types.ts +
  infinity-web App.tsx field renames — including the App.tsx conflation
  UserInput { session_id: p.thread_id } which the rename makes honest

BREAKING CHANGE: daemon wire protocol field renames (session_id family);
old clients/daemons cannot interop across this version for the renamed
messages. TS clients updated in the same change.

Deferred to the &ThreadId loosening rebase: Stage-3's new &ThreadId
params (handle_emigrate, connect_remote_session, load_toolsets, etc.).

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View logs

[Copilot]

🟡 Changes recommended

There are confirmed runtime-safety/API-correctness issues (UTF-8 byte slicing panics in TUI rendering and inconsistent/unsafe handling of ThreadRef/remote naming/parsing) that should be addressed before approval.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR is stage 3 of the string-ID → typed-ID migration, implementing the decision that a session is its root thread by renaming session_id → root_thread_id across the daemon wire protocol and introducing ThreadRef / RemoteName to replace ad-hoc "remote/uuid" composite strings while keeping the serialized value format stable.

Changes:

• Refactors infinity-protocol message schemas and shared data types to use ThreadRef and typed RemoteName, with protocol field renames for the session/root-thread family.
• Updates Rust daemon + sub-agents (Slack bot, CLI/ACP, Lambda, RAP bridge/client) to use typed thread IDs in APIs and internal maps, removing string-splitting logic for remote-prefixed IDs.
• Updates TypeScript clients (infinity-web, infinity-ui) to the new JSON field names/types.

File summaries

File	Description
infinity-web/src/App.tsx	Updates client message field names (session_id → root_thread_id) and related handling for connect/migrate flows.
infinity-ui/src/types.ts	Updates TS wire types for renamed fields and SwitchModel’s corrected thread_id naming.
crates/rap-client/src/toolset_loader.rs	Switches toolset-loading APIs to typed ThreadId<str> parameters.
crates/rap-client/src/notifier.rs	Switches notifier APIs to typed ThreadId<str> parameters.
crates/infinity-slack-bot/tests/dataflow_sim.rs	Updates test fixtures to new protocol field names and ThreadRef types.
crates/infinity-slack-bot/src/session_store.rs	Stores Slack thread→session mapping as ThreadRef while preserving on-disk JSON format.
crates/infinity-slack-bot/src/flow.rs	Adapts Slack dataflow to root_thread_id naming in Connected.
crates/infinity-slack-bot/src/daemon_sidecar.rs	Types daemon commands with ThreadRef and updates Connected/UserInput handling.
crates/infinity-slack-bot/src/daemon_client.rs	Types daemon client APIs with ThreadRef and updates connect/send input payloads.
crates/infinity-rap-bridge/src/lib.rs	Switches RAP bridge connect API to typed ThreadId<str>.
crates/infinity-protocol/src/lib.rs	Introduces RemoteName + ThreadRef and applies protocol-wide field/type renames to use typed IDs.
crates/infinity-protocol/Cargo.toml	Adds strkind dependency for new typed string kinds.
crates/infinity-daemon/tests/rap_callback_flow.rs	Updates daemon tests to ThreadRef/root_thread_id protocol changes.
crates/infinity-daemon/tests/keep_alive.rs	Updates keep-alive tests to ThreadRef and typed ID generation.
crates/infinity-daemon/src/session/tests.rs	Updates session manager tests for HashMap<ThreadRef, SessionInfo> session maps.
crates/infinity-daemon/src/session/observer.rs	Emits ThreadRef in replay/history messages instead of string IDs.
crates/infinity-daemon/src/session/mod.rs	Updates session manager wire messages and session listing maps to ThreadRef.
crates/infinity-daemon/src/session/display.rs	Updates display/event conversion to attribute messages with ThreadRef.
crates/infinity-daemon/src/remote.rs	Types remote configs/maps with RemoteName/ThreadRef and replaces string prefixing with ThreadRef ops.
crates/infinity-daemon/src/rap_servers.rs	Updates broadcast thread_id to ThreadRef.
crates/infinity-daemon/src/migrate.rs	Refactors migration orchestration to typed ThreadRef/RemoteName and removes composite-string juggling.
crates/infinity-daemon/src/memory_store.rs	Updates thread tree/session info to store ThreadRef for thread relationships.
crates/infinity-daemon/src/ids.rs	Changes IdSource::generate() to return typed ThreadId.
crates/infinity-daemon/src/client_handler.rs	Replaces remote-id string surgery with ThreadRef prefix/strip operations and updates message routing.
crates/infinity-agent-lambda/src/event_handler.rs	Updates toolset loading callsites to pass typed thread IDs.
crates/infinity-agent-cli/tests/tui_snapshots.rs	Updates CLI snapshot test events to carry ThreadRef.
crates/infinity-agent-cli/tests/tui_reflow_snapshots.rs	Updates snapshot test session maps to use ThreadRef keys.
crates/infinity-agent-cli/tests/tui_flow_snapshots.rs	Updates CLI flow tests for ThreadRef-typed session IDs in events/maps.
crates/infinity-agent-cli/tests/common/mod.rs	Updates harness types/channels to use ThreadRef instead of String IDs.
crates/infinity-agent-cli/src/terminal.rs	Keys terminal state/maps by ThreadRef and updates display attribution handling accordingly.
crates/infinity-agent-cli/src/session_picker.rs	Types session picker IDs as ThreadRef and updates rendering logic.
crates/infinity-agent-cli/src/main.rs	Updates remote config creation/checks for typed RemoteName.
crates/infinity-agent-cli/src/daemon_client.rs	Updates daemon client wiring and --session prefix matching for ThreadRef.
crates/infinity-agent-cli/src/acp_server.rs	Types ACP↔daemon session bookkeeping with ThreadRef on the daemon side while preserving ACP string IDs.
Cargo.lock	Records the new strkind dependency in the lockfile.

Review details

Suppressed comments (1)

crates/infinity-daemon/src/client_handler.rs:374

• Same issue here: defaulting a missing active_remote_name to an empty RemoteName can cause incorrect stripping/prefixing and masks an invariant violation. Consider expecting the remote name when remote_proxy_tx is set, instead of synthesizing one.

                    let rn = active_remote_name.clone().unwrap_or_else(|| "".into());
                    match &msg {

• Files reviewed: 34/35 changed files
• Comments generated: 6
• Review effort level: Lite

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[shadaj]

All the other Copilot comments are correct but also somewhat irrelevant, so up to you if you want to address here or later.

[MingweiSamuel]

I will put in separate PR