fix(chat): new-chat stale selection + blank thread header entering created conversations

[chrisnojima]

Problem

Two bugs in the new-chat flow:

1. Stale selection: open new chat → pick a user → Start → reopen new chat: the previous user is still selected.
2. Blank header: entering the conversation created by this flow often leaves the navigation header blank until you press back.

Root causes / fixes

Stale selection — the team-building store is a per-namespace singleton that outlives the modal. finishedTeamBuilding deliberately preserved teamSoFar, and the blur-listener cleanup (CancelOnBlur) doesn't fire when the modal is removed, so the selection leaked into the next session.

• finishedTeamBuilding now clears the selection for every namespace except teams (whose add-members error path re-opens the builder and relies on the chips being intact; every onComplete handler receives a copied set, so nothing else reads the store after finish).
• The builder screen also resets stale non-teams selections on mount, covering the back-out path.

Blank header — the pendingWaiting → real-conversation switch went through navigateAppend's replace, which degrades to setParams for the same route name. That keeps the native screen alive, and its header title was measured while pendingWaiting rendered it empty — iOS never re-measures an initially-empty title subview. Instrumentation confirmed the JS side was fully healthy (title rendered and laid out at 105pt) and the existing one-shot setOptions reconfigure fired, yet the bar stayed blank.

• navigateToThread now dispatches a real StackActions.replace for this case, so the fresh screen measures the title with its content already present.
• BadgeHeaderUpdater moved outside the conversation-keyed provider so its title-was-empty tracking survives same-screen conversation swaps.
• The header title component now arms ensureConversationMetaLoaded itself, so the header self-heals for any conversation whose meta never loaded.

Tests

• New store test: chat-namespace finish clears the selection; existing teams-preservation test unchanged.
• yarn lint, yarn tsc, yarn jest stores/tests/team-building.test.ts all green.

[Copilot]

Pull request overview

Fixes two regressions in the new-chat flow: (1) stale user/team selection persisting across re-opening the team builder, and (2) an intermittently blank iOS conversation header when transitioning from pendingWaiting to the real conversation.

Changes:

• Reset team-building state for non-teams namespaces both on finishedTeamBuilding and on builder mount to prevent stale selection leakage.
• Force a true React Navigation StackActions.replace when transitioning pendingWaiting → real conversation to ensure iOS re-measures the header title.
• Make the header more resilient by keeping BadgeHeaderUpdater alive across same-screen conversation swaps and having the header arm ensureConversationMetaLoaded directly.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
shared/team-building/page.tsx	Resets non-teams team-builder state on mount to avoid stale chips across modal re-opens.
shared/stores/tests/team-building.test.ts	Adds coverage verifying finishedTeamBuilding clears selection/error for chat namespace while preserving teams behavior.
shared/stores/team-building.tsx	Updates finishedTeamBuilding to clear selection outside teams, keeping teams selection preservation intact.
shared/constants/router.tsx	Uses StackActions.replace for pendingWaiting → real conversation to avoid header blanking caused by setParams.
shared/chat/conversation/header-area/index.tsx	Ensures conversation meta is loaded from the header to self-heal missing title data.
shared/chat/conversation/container.tsx	Moves BadgeHeaderUpdater outside the conversation-keyed provider so its “title was empty” tracking survives param-based swaps.