Runtime warns CLAUDE.md is over the 150.0k-char limit (v2.1.259) but the docs do not mention a 150k limit

## Summary

At session startup, when the user `CLAUDE.md` is large, Claude Code v2.1.259 prints:

```
/Users/.../CLAUDE.md is over the 150.0k-char limit (179.0k chars) · /memory to free up context
```

But the documentation never mentions a 150k-character limit. `memory.md` says "target under 200 lines" and notes that a file over 4 MiB is skipped entirely. Older material (#56406, Aug 2026) cites a **40,000**-character warning threshold, which appears to have been raised to **150,000** since. Users cannot reconcile the shipped warning with the docs -- and the "150k" figure also collides with the auto-compact token window (#85205), which is a different thing.

## Evidence

Startup banner, Claude Code v2.1.259:

```
/Users/.../CLAUDE.md is over the 150.0k-char limit (179.0k chars) · /memory to free up context
```

## Request -- please document, for the current version:

1. The actual `CLAUDE.md` size-warning threshold (150.0k characters in v2.1.259), and whether it scales with the context window (see #56406).
2. Whether crossing it truncates or merely warns. The banner suggests `/memory to free up context` (a context-cost warning), while separate guidance says the file loads in full below the 4 MiB hard skip -- please confirm the two coexist and that content is not silently dropped.
3. Distinguish this **character** limit from the auto-compact **token** window (#85205), which shares the "150k" number and confuses users.

Prior art: #56406, #85205.

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

Begin with memory.md and the startup warning described in the issue; compare the documented 200-line guidance and 4 MiB skip behavior with current runtime evidence. Update the documentation to state the v2.1.259 character-warning threshold, scaling and truncation behavior, and distinguish it from the token window in #85205; done when users can reconcile the banner with the docs.

由索引模型根据 Issue 内容生成。