fix(auth): show the account occupying a config dir after an in-place switch-account

[andrei-hasna]

What

accounts switch-account switches a session's account in place: it swaps the live auth files inside the config dir and records the new occupant in .accounts-auth/switched-account.json — without moving the dir or re-pointing the registry. The statusline resolved the session profile from the registry entry keyed by dir, or from the dir's path name. Both describe the dir's owner, so after a switch the statusline kept rendering the old account indefinitely (PR #8 made resolution per-session, but per-session resolution still named the dir owner, not the dir occupant).

This PR reads the occupant marker and lets it win over both the registry and the layout name — for the auth-profile segment and the registry-email fallback in sessionAccountEmail. The session's own live state file (.claude.json → oauthAccount.emailAddress) still wins for the email, since it is what the session actually authenticates as. When the marker is cleared (owner restored or fresh login), resolution falls back to the owner exactly as before.

Root-cause evidence (real machine state, spark02)

The dir ~/.hasna/accounts/profiles/claude/account088 was really switched on 2026-07-29:

• live .claude.json oauthAccount.emailAddress = the occupant account's email
• .accounts-auth/switched-account.json = { "profile": "account033", ... }
• .accounts-auth/oauth-account.json = the parked owner identity

Rendering against that dir:

build	first line
installed 0.0.4 (before)	account088 · hasna (stale)
this branch	account033 · hasna (the actual occupant)

Three dirs rendered simultaneously with this branch: account088→account033, account002→account002, account030→account033 — sessions on different accounts differ; dirs genuinely occupied by the same account agree.

On "same statusline across sessions"

Sessions sharing one config dir rendering identically is accurate, not a display collapse: the dir is shared auth state, and an in-place switch flips every session bound to it together (accounts says so itself: "3 live sessions share this config dir; all of them switch together"). After fleet account rotation, several dirs are genuinely occupied by the same account, so identical statuslines across those sessions are the truth — previously they were identical and stale.

Tests

• TDD: 8 new tests written first, 6 failed on unfixed code (positive control), all 183 pass after: switch flip, occupant-over-layout, nameless occupant suppresses stale owner name, marker clear restores owner, corrupt marker degrades, two dirs differ simultaneously, occupant email beats owner registry email, live state file still beats marker email.
• bun run typecheck RC=0, bun test RC=0 (measured unpiped), bun run build RC=0.

Notes

• The marker filename mirrors @hasna/accounts' claude-layout module, which owns it but exports no public reader; the code comment marks it for replacement via the same lazy import used for the registry paths if one appears. This matches the existing idiom in src/accounts.ts (registry filename/layout constants documented as the owning package's defaults).
• No dependency changes.

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