Build pecos-stab-tn at opt-level 2 in dev and test profiles like the other simulation crates

[ciaranra]

Why

After #683/#684 the PR gate's critical path is pr-core-rust, and inside it the workspace test phase: 2486 CPU-seconds of test work on a 4-core runner, ~10.4 min however it is scheduled (a nextest trial, #698, confirmed the phase is CPU-bound, not serialization-bound). The two largest contributors are the surface-code LER equivalence test and the pecos-stab-tn test binaries. The root Cargo.toml already builds the simulation crates at opt-level = 2 in dev/test builds for exactly this reason, but pecos-stab-tn was not on the list, so its tensor-network code ran unoptimized under test.

Measured locally (14 cores):

	opt-level 0 (today)	opt-level 2
pecos-stab-tn lib tests (352)	159 s	5.6 s
all pecos-stab-tn test targets (lib, verification, exact_default_measurement)	~220 s serial on CI	8 s
extra compile for the crate		~33 s

Also tried [profile.dev.package."*"] opt-level = 2 for every external dependency: no further gain on stab-tn, 6% on the LER test, and every dependency recompiles slower. Not taken.

What

One entry in the existing [profile.dev.package.*] block plus a comment with the numbers. profile.test inherits the per-package overrides (verified by reading the rustc invocations: -C opt-level=2 for the listed crates in cargo test builds). Debug assertions stay on. Crates that depend on pecos-stab-tn (the stab-mps and mast Selene plugins, pecos-rslib-exp, benchmarks) get the optimized crate in their debug builds.

Verification

• cargo test --locked -p pecos-stab-tn with the change: lib 352 passed / 8 ignored, verification 95 passed / 9 ignored, exact_default_measurement 9 passed / 20 ignored; 46 s wall including the 37 s compile.
• pre-commit on Cargo.toml: clean.
• Measured on CI (gate run 33901282224, warm Rust cache): pr-core-rust 17 min end to end, down from 25 min on the previous warm-cache run and ~30 min before Cut ~20 min of wasted native builds from the Python CI lanes and make the PR-gate Rust caches restorable #683. Workspace test phase 5.1 min (per-binary times sum to 284 s, was 656 s; longest binary is now the LER test at 191 s), follow-up phases 1.6 min, compile 6.6 min.