M1: the choudoufu probe accepts the estate.chdf.hcl sidecar (#386)

[lex00]

Child of #386, M1.

What does not work

src/choudoufu-member.ts's hasLiveBlock is the choudoufu member's probe (choudoufuSpec.probe, src/choudoufu-live.ts): a regex ^\s*live\s*\{ over the root's *.tf files. choudoufu's leading declaration is now the sidecar:

# estate.chdf.hcl
estate = "prod-networking"

record_store "ssm" {
  key_prefix = "tofu-records/prod-networking"
}

(choudoufu site/content/docs/use/reference.md, "Two places to write it, one dialect"; the live block inside terraform {} remains supported, both at once is an error.) Every tools/estate-gen cohort and every migrated terralith uses the sidecar. Rendered the s3 cohort and ran behold doctor on it: "no chant.config.ts here, and no estate members declared". memberKindOf returns undefined for it.

What to build

• The probe accepts either form: estate.chdf.hcl present in the directory, or a root *.tf with a live { block. Rename to what it now means (isChoudoufuEstate or similar); update the call sites that import hasLiveBlock (src/choudoufu-live.ts, src/server.ts) and the expects text: "an estate.chdf.hcl sidecar or a live { estate = … } block in a root *.tf file".
• The doctor line and AGENTS.md's "Adding a member kind" example (a regex over a root file) and the choudoufu member's own doc comments say sidecar first.
• No -estate flag anywhere: choudoufu reads the sidecar itself, and -estate beside a declaration is refused (src/choudoufu-live.ts header).

Definition of done

• src/project.test.ts (the probe and the object form) and src/choudoufu-member.test.ts cover: sidecar only, live block only, both absent, a .tf mentioning live { in a comment is NOT a false positive only if it already was not (keep the current regex behaviour, do not widen it).
• behold doctor on a directory holding only estate.chdf.hcl and *.tf reports the choudoufu member, not "no chant.config.ts".
• just check green.

[lex00]

Merged in #392 (072480e), released in @intentius/behold@0.18.0.