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/src/lib.rs

@@ -6,6 +6,7 @@ pub mod prompt;
 pub mod gate_parser;
 pub mod gated_loop;
 pub mod query_executor;
+pub mod optimizer;
 
 pub use gate_parser::{GateResponse, ParseError, parse_gate_response};
 
@@ -19,3 +20,4 @@ pub use lesson::{
 pub use query::{Query, QuerySet, SynthesisQuery};
 pub use prompt::{PromptBuilder, PromptMessages};
 pub use symptom_projection::{project_symptom, SymptomVector};
+pub use optimizer::{ContextOptimizer, ContextOptimizerConfig, ContentType, OptimizedChunk};