✨ feat(kebab-cli): error_classify dispatcher + wire helpers (fb-27)

`error_classify::classify` maps anyhow::Error → ErrorV1 wire record by
downcasting to known typed errors (LlmError + ConfigInvalid + NotIndexed
re-exported from kebab_app::error_signal, plus std::io::Error chain).
Generic fallback emits `code: "generic"` with the chain in `details` when
verbose.

wire.rs adds wire_schema (idempotent re-tag, mirrors wire_doctor pattern
since SchemaV1 carries its own schema_version field) and wire_error_v1
(simple tag_object). Tests pin both wrappers + 7 classify code paths.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/kebab-cli/Cargo.toml

@@ -28,6 +28,7 @@ kebab-eval = { path = "../kebab-eval" }
 # launches it.
 kebab-tui    = { path = "../kebab-tui" }
 anyhow       = { workspace = true }
+serde        = { workspace = true }
 serde_json   = { workspace = true }
 clap         = { version = "4", features = ["derive"] }
 # p9-fb-02: ingest progress UI.
@@ -43,3 +44,6 @@ ctrlc        = "3"
 
 [dev-dependencies]
 tempfile     = { workspace = true }
+# llm_unreachable_classifies_to_model_unreachable test needs a real
+# reqwest::Error (private constructor) — built from a connect-refused call.
+reqwest      = { version = "0.12", default-features = false, features = ["blocking", "rustls-tls"] }