Add split readiness doctor (#723)
Validation
* Validation tier: Tier 4 - split-readiness verification tooling, read-only management diagnostics, Windows capture helper, and post-review diagnostic correctness repair; no routing, wire protocol, or model-load behavior change.
* git fetch --no-tags origin main:refs/remotes/origin/main: PASS, origin/main at 6f6d606c61.
* git rebase origin/main: PASS, no conflicts.
* git diff --check: PASS, no output.
* git diff --cached --check: PASS, no output.
* cargo fmt --all -- --check: PASS, no output.
* LLAMA_STAGE_BUILD_DIR=/Users/Funtland/Downloads/mesh-llm/.deps/llama-build/build-stage-abi-metal cargo test -p mesh-llm-host-runtime split_readiness --lib -- --test-threads=1: PASS, 9 passed.
* LLAMA_STAGE_BUILD_DIR=/Users/Funtland/Downloads/mesh-llm/.deps/llama-build/build-stage-abi-metal cargo check -p mesh-llm: PASS.
* LLAMA_STAGE_BUILD_DIR=/Users/Funtland/Downloads/mesh-llm/.deps/llama-build/build-stage-abi-metal /opt/homebrew/bin/cargo-clippy clippy -p mesh-llm-host-runtime --all-targets -- -D warnings: PASS.
* Ledger: not applicable - not required for selected validation tier/change family.
* Version: not applicable - diagnostics/tooling/docs only; no release/version sync required.
* Not run: pwsh syntax/help validation - pwsh is not installed in this environment.
* Not run: live two-node split smoke - no local split-capable multi-node runtime/model endpoint was available; deterministic split-readiness tests cover the diagnostic classification and capture path.
Rollback
* git revert HEAD
07b9dea178