Signed-out startup header shows an expired promotional notice and asserts "API Usage Billing" with no credential (v2.1.266)

## Summary

On a fresh launch of v2.1.266 with no credential present, the startup header shows two wrong things at once: a promotional notice whose own end date passed seven weeks ago, and a billing mode (`API Usage Billing`) on the same screen that says `Not logged in`.

## Evidence

Linux, 2026-09-09. The host had just auto-updated from 2.1.150; the session came up signed out. Startup header, verbatim:

```
Claude Code v2.1.266
Opus 5 (1M context) · API Usage Billing
~/...

Updated to latest. Got 65 features, 397 bugfixes, and 152 other changes.
code.claude.com/docs/en/changelog for details

Extended through July 19
We're extending Claude Fable 5 access on all paid plans, as well as keeping
Claude Code's weekly rate limits 50% higher, through July 19.

As before, you can use up to half of your weekly usage limit on Fable 5. After
that, you can keep using Fable 5 with usage credits, or switch to another model
to keep working within your remaining limits.

More details here: https://support.claude.com/en/articles/15424964-claude-fable-5-promotional-access
```

and, in the lower right of that same screen:

```
Not logged in · Run /login
```

## Issue 1 -- a promotional notice rendered past its own expiry

The notice announces an extension "through July 19" and was displayed on **September 9**, about seven weeks after the date it names. Either it is being served past its expiry or it is cached client-side and never revalidated. A promo whose stated end date has passed should not render at all.

## Issue 2 -- "API Usage Billing" asserted with no credential

The same screen reports a billing mode and reports being signed out. There was no credential of any kind to bill against: `ANTHROPIC_API_KEY`, `ANTHROPIC_AUTH_TOKEN`, `CLAUDE_CODE_USE_BEDROCK` and `CLAUDE_CODE_USE_VERTEX` were all unset, and `~/.claude/settings.json` carried no key-bearing setting.

Whatever the header falls back to when signed out, `API Usage Billing` is a misleading default. It reads as a statement that this session will be billed as metered API usage -- an alarming thing for a subscription user to see, and here not true of anything. Showing no billing line while signed out, or an explicit placeholder, would be clearer.

Possibly related: #62338, where the billing mode shown by Claude Code did not match what was actually being billed. This report is only about the display being wrong on a signed-out session -- no unexpected billing occurred here -- but it is the same class of "the header asserts a billing mode you cannot verify".

## Note

Both were observed on the same screen and appear to share a cause (the signed-out startup path), so they are filed together. Happy to split them if you would rather track them separately.

---
_Filed via Claude Code on the user's behalf._

Reproduce the signed-out startup path on Linux and search the startup header for the exact strings “Extended through July 19” and “API Usage Billing.” Verify that an expired promotional notice is suppressed and that no billing mode is asserted when the screen also says “Not logged in · Run /login”; the issue names no files or tests to start from.

索引モデルが issue の本文から書いたものです。