cratify: extract 5 ccft crates, add lib facade

[adiled]

What

Extract the reusable, generic logic out of the ccft binary into five cratified sub-crates, and turn the root ccft into both a binary and a library facade that re-exports them.

Crates

• ccft-ledger — append/tail/range-read a growing JSONL ledger (Record, TailReader, parse_range, percentile, coverage)
• ccft-session — session-id extraction from hyper headers + JSON metadata bodies
• ccft-lex — pure text fingerprinting: lexical stats, content bigrams, novelty, system-block stripping
• ccft-brainrot — agentic turn classification, EM gap mixture, baseline fingerprint, driver/bot scoring
• ccft-sse — generic hyper Body tap for OpenAI/Anthropic SSE + non-stream JSON token/usage accounting

Library facade

src/lib.rs re-exports the five crates so downstream Rust code can
use ccft::{ledger, lex, sse}; without depending on each crate individually:

let r = ledger::parse_range("24h")?;
let (ttr, _, _) = lex::lexical_stats(text);
assert_eq!(sse::PROVIDER_OPENAI, "openai");

The binary's own modules (handler/config/lifecycle/…) stay ccft-specific and are not part of the library surface.

Verification

• cargo build --workspace green
• 24 tests pass (1 lib facade + 8 bin + 5 brainrot + 2 ledger + 5 lex + 3 sse)
• All 5 crates clippy-clean (bin retains only ~30 pre-existing warnings)
• Bin depends on exactly the 5 crates + ops; re-export layer is thin (path glue/adapters), no duplicated implementation logic