feat: M3.8.1 phase 1 — content router + log compressor

ContentRouter uses Google Magika ML for content detection (<1ms) with regex
fallback. Detects JSON, code, logs, diffs, config, text.

LogCompressor reuses M3.7.7 patterns (markers, cascade, strip_ansi) to
shrink build logs by keeping errors/stacks and dropping noise.

17 unit tests passing:
- router: json, code, diff, log, text detection
- log: error lines, stack traces, ansi stripping, compression
- optimizer: token estimation, passthrough mode

Magika + ort ONNX runtime added to Cargo.toml.

crates/mem-core/Cargo.toml

@@ -2,6 +2,7 @@
 name = "mem-core"
 version = "0.1.0"
 edition = "2021"
+publish = false
 
 [dependencies]
 tokio = { workspace = true }
@@ -15,3 +16,6 @@ sha2 = { workspace = true }
 tracing = { workspace = true }
 hex = "0.4"
 time = { version = "0.3", features = ["serde", "formatting", "parsing", "macros"] }
+magika = "1.1.0"
+ort = { version = "2.0.0-rc.12", default-features = true }
+regex = "1.10"