refactor(channel): run target-message on createMachine

[synoet]

Why

createTargetMessageController already runs a deep-link lifecycle (navigate → load around → scroll → flash → release). That lifecycle lived in five independent | undefined fields, then in a five-phase Mealy table with two world-to-event effects. Both encodings made readiness a state and left a race: ChannelThread can ack a root-only target before a viewport-ready effect fires, and the five-phase table ignored that ack.

This rewrite writes the machine down as three states and tests it as values. Readiness is a derivation. The flash timer is a state-scoped lifetime. There are no createEffects.

What landed

@macro-inc/machine (packages/machine)

• MachineDef<S, E, C> — one required entry per state; on returns { state, commands? } or undefined (ignored). No dispatch in on.
• createMachine — signal + per-state scopes (dispose/remount on every transition, including same-t new payload) + execute commands + serialized dispatch with a cycle cap.
• step / simulate — pure table helpers. No Solid, no timers.
• nix-support/node_modules-hashes.json updated so the fixed-output .#js-node-modules tree includes the new workspace package.

Target-message machine (apps/web/src/features/channel/Channel/target-message.ts)

Lives next to the controller, same as other Channel helpers. Events and selectors are exhaustive ts-pattern matches.

• States: idle | targeting | flashing, each carrying orthogonal loadAround.
• Events: navigate, root-scroll-done, reply-scroll-done, flash-elapsed, pagination-restored, release, reset.
• One command: restore-default-pagination, emitted on the ack → flashing arrow when an around-query is anchored. Cleared only by a successful restore handshake or reset.
• Selectors encode the ChannelThread contract. A root-only target stays pending until ack (readiness does not clear it). A nested target's root row clears on readiness so the reply scroll is the only viewport movement.

Controller (create-target-message-controller.ts)

• Public API unchanged, including #6080's hasPendingElementScroll.
• Channel.tsx / ThreadList untouched.
• Flash timer lives in the flashing scope (onCleanup cancels on navigate / release / reset / unmount).
• Readiness is a function over navigation, didInitialScroll, and messageKeys — not a memo, because Channel.tsx constructs the controller before messageIndex exists.
• goToMessage untracks messageKeys and ready.

Behavior change

Restore moves from "viewport ready, before the scroll" to "after the scroll is acknowledged." Between those moments Channel.tsx keeps sourcing from the around query — which it already did for the whole pre-ready window. loadAroundMessageId still selects useChannelMessagesQuery; the missing-message effect still watches it; threadPaginator still wraps that query.

An early root ack now does restore (the original skipped that path). By the time a row can ack it is mounted, so the around data is present.

Tests

• Primitive: disposal order, self-transition remount, queued dispatch from scope/command/cleanup, cycle error, post-dispose no-op, matches — 15.
• Machine: it.each tables per event, ChannelThread selector table, simulate sequences (root, nested with ignored root ack, rapid-nav, failed restore, mid-flight reset) — 48.
• Container: timer lifetime, readiness derivation, cache restore on ack, construct-time TDZ — 9.

72 tests passed locally. Machine and container ran against solid-js's browser build. This Cloud VM cannot start the apps/web vitest workspace runner (EINVAL: scandir '//proc/.../net' during project init); CI's bunx vitest from apps/web includes the new machine project plus --project channel.

Out of scope

• No changes to Channel.tsx, ThreadList, or clearStaleRestoredChannelData.
• Email undo-send and ThreadList initial-scroll are the next createMachine candidates, not this PR.

  

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📒 Files selected for processing (4)

• apps/web/src/features/channel/Channel/create-target-message-controller.ts
• apps/web/src/features/channel/Channel/tests/create-target-message-controller.test.ts
• apps/web/src/features/channel/domain/target-message.test.ts
• apps/web/src/features/channel/domain/target-message.ts

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📝 Summary

Summary by CodeRabbit

• Bug Fixes

  • Improved navigation to targeted messages and replies in channels.
  • Added more reliable scrolling, highlighting, and flash behavior when entering or changing targets.
  • Improved pagination restoration after loading targeted messages.
  • Prevented stale or mismatched navigation events from affecting the current view.

• Tests

  • Expanded coverage for target-message navigation, scrolling, highlighting, cleanup, and viewport readiness.

Walkthrough

Target-message navigation now uses a reducer-based state machine with loading, viewport-waiting, scrolling, and flashing states. The controller dispatches navigation and scroll events, executes flash and pagination commands, and reacts to message-key and initial-scroll signals. Tests cover reducer transitions, selectors, stale events, deduplication, flash cleanup, target loading, and viewport readiness.

Merge Risk: ⚪ Minimal · up to c9d7f

This refactor makes target-message navigation transitions explicit while preserving the existing controller interface and client-side scope. No actionable merge-blocking risk remains after normal checks and review.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title uses valid Conventional Commits format with the refactor(channel) prefix, describes the state-machine change, and is 69 characters long.
Description check	✅ Passed	The description clearly explains the reducer state machine, controller refactor, scope, tradeoffs, testing, and verification limitations. It is directly related to the changeset.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[github-actions]

Preview: https://synoet-target-message-state-ma-rk3uc1.preview.macro.com/app (105ed2e)

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