fix(deps): pin rand 0.9 to match ndarray-rand 0.16 — un-break workspace build (#129)

## `main`'s Rust workspace does not compile — this fixes it

`crates/esn` and `crates/lsm` fail to build on `main`. A dependabot bump
set `rand = "0.10"` in the workspace `Cargo.toml`, but **`ndarray-rand
0.16` bundles `rand 0.9`** — so two incompatible `rand` crates end up in
the tree and the `Normal`/`Bernoulli` distributions and `Rng` trait no
longer line up (`E0277`), plus `random()`/`sample()` appear "moved"
(`E0599`).

**This went undetected because `rust-ci` dies at startup (0 jobs)** —
the estate `rust-ci-reusable` is broken (separate, upstream issue in
`hyperpolymath/standards`), so nothing actually compiled the workspace
in CI.

### Fix
Revert `rand` → `0.9` and `rand_distr` → `0.5` (the line `ndarray-rand
0.16` expects). No source changes needed; the committed `Cargo.lock`
already resolves rand 0.9, so only `Cargo.toml` drifted.

### Verified locally
- `cargo build --workspace` → Finished
- `cargo test --workspace` → all green
(esn/lsm/bridge/sensors/core/claude-client + proptests +
lifecycle/concurrency), 0 failures.

This unblocks every open gossamer sub-PR draft (#121–#128), whose
workspace verification was failing on this exact pre-existing break.
**Recommend merging first.** (`rust-ci` itself will stay red until the
`standards` reusable is fixed — tracked separately.)

https://claude.ai/code/session_01Gu1JFCZHuBtBhAWPr4sMQw

---
_Generated by [Claude
Code](https://claude.ai/code/session_01Gu1JFCZHuBtBhAWPr4sMQw)_

Co-authored-by: Claude <noreply@anthropic.com>

Author: hyperpolymath

Cargo.toml

@@ -22,8 +22,12 @@ repository = "https://github.com/hyperpolymath/neurophone"
 # Core neural network
 ndarray = { version = "0.17", features = ["rayon", "serde"] }
 ndarray-rand = "0.16"
-rand = "0.10"
-rand_distr = "0.6"
+# rand pinned to 0.9 / rand_distr 0.5 to match ndarray-rand 0.16 (which bundles
+# rand 0.9). A dependabot bump to rand 0.10 broke the build: rand 0.10 is a
+# separate, incompatible rand in the tree (Distribution/Rng traits don't match
+# ndarray-rand's). Revert until ndarray-rand ships a rand-0.10-compatible release.
+rand = "0.9"
+rand_distr = "0.5"
 rayon = "1.12"
 
 # Serialization