Build/cache native modules

[Dreamsorcerer]

Problem

nav_stack tests are being skipped due to lack of native modules.

Solution

Build the modules in CI, cache the nix build in Cachix.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

Flag	Coverage Δ
OS-ubuntu-24.04-arm	63.85% <ø> (ø)
OS-ubuntu-latest	64.70% <ø> (ø)
Py-3.10	64.68% <ø> (-0.01%)	⬇️
Py-3.11	64.69% <ø> (ø)
Py-3.12	64.69% <ø> (+<0.01%)	⬆️
Py-3.13	64.69% <ø> (+<0.01%)	⬆️
Py-3.14	64.70% <ø> (ø)
Py-3.14t	64.69% <ø> (+<0.01%)	⬆️
SelfHosted-Large	30.34% <ø> (-0.01%)	⬇️
SelfHosted-Linux	38.89% <ø> (+0.61%)	⬆️
SelfHosted-macOS	36.99% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ation/nav_stack/modules/far_planner/far_planner.py	97.33% <ø> (ø)
...n/nav_stack/modules/path_follower/path_follower.py	95.45% <ø> (ø)
...stack/modules/terrain_analysis/terrain_analysis.py	96.15% <ø> (ø)

... and 8 files with indirect coverage changes

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[greptile-apps]

Greptile Summary

This PR wires up a new nav-stack-natives CI job that builds the three nav_stack native modules (far_planner, path_follower, terrain_analysis) via Nix and pushes the results to a Cachix cache, then teaches the self-hosted test job to pull from that cache before running skipif_no_ros tests.

• New bin/build-nav-stack-natives script discovers NativeModuleConfig subclasses, skips modules whose executables already exist, and builds the rest in parallel with ProcessPoolExecutor.
• install-nix.sh hardening: adds bash default assignments for all INPUT_* vars so the script is safe to call from a plain run: step without a composite action.
• Version bumps for all three native module flake references (far_planner v0.5.0→v0.7.1, path_follower v0.2.0→v0.2.1, terrain_analysis v0.1.1→v0.1.2).

Confidence Score: 4/5

Safe to merge once the macOS test-blocking dependency is addressed; the remaining findings are low-impact edge cases.

The macOS self_hosted matrix variant is now coupled to nav-stack-natives even though it never installs Nix or fetches native modules. A Cachix auth failure or nix build timeout would cancel the macOS run entirely, silently dropping coverage that has no dependency on native builds.

ci.yml — the needs: [compute-ros-pin, nav-stack-natives] line on self-hosted-tests couples both matrix variants to native module availability.

Important Files Changed

Filename	Overview
.github/workflows/ci.yml	Adds nav-stack-natives job for building/caching native modules; makes self-hosted-tests depend on it at the whole-job level, inadvertently blocking the macOS matrix variant (which has no native-module dependency) when the build job fails
bin/build-nav-stack-natives	New script to discover and parallel-build NativeModuleConfig subclasses; ProcessPoolExecutor(max_workers=0) crash path exists if discover() returns empty
docker/ros/install-nix.sh	Adds bash default-value assignments for INPUT_* env vars so the script can be invoked from a plain workflow run: step without a composite action
dimos/navigation/nav_stack/modules/far_planner/far_planner.py	Version bump for far_planner nix flake reference: v0.5.0 → v0.7.1
dimos/navigation/nav_stack/modules/path_follower/path_follower.py	Version bump for path_follower nix flake reference: v0.2.0 → v0.2.1
dimos/navigation/nav_stack/modules/terrain_analysis/terrain_analysis.py	Version bump for terrain_analysis nix flake reference: v0.1.1 → v0.1.2
docs/usage/native_modules.md	Adds a section documenting the Cachix substituter opt-in for local development with the correct public key

_{Reviews (3): Last reviewed commit: "Merge branch 'main' into sam/native-modu..." | Re-trigger Greptile}