fix(photon): resolve the Hermes-managed Node for the sidecar

[Drexuxux]

What

On an install whose Node is the Hermes-managed one, the Photon platform never works — and stays broken on every run.

$HERMES_HOME/node is not on an arbitrary process's PATH; only generated service units get it prepended. Photon resolved node and npm with bare shutil.which() at five sites, so all five resolved nothing:

site	effect
adapter.py check_requirements()	photon reports unavailable — the gateway never creates the adapter
adapter.py npm gate + _reinstall_sidecar_deps()	gives up before running npm; deps never installed
adapter.py _node_bin	spawn falls back to the literal "node" → FileNotFoundError
cli.py install-sidecar	refuses to run: "npm is not on PATH"
cli.py status	prints ✗ missing (install Node 18+)

That is exactly the population the installer provisions a managed Node for: system Node/npm missing, or below the engines floor.

Reproduced with a managed tree present and no system Node on PATH:

managed node dirs       : ['<home>/node', '<home>/node/bin']
managed node present    : True

adapter.py -> _node_bin : 'node'
  spawn                 -> FileNotFoundError
cli.py install-sidecar  : npm is not on PATH -> exit 1
cli.py status           : 'missing (install Node 18+)'

25d0bcd42 fixed this class across 11 files and tests/test_managed_runtime_resolution.py guards it, but that guard's _EXEMPT_DIRS skips plugins/ — so the platform adapters were never swept.

Fix

Route the five sites through hermes_constants.find_node_executable(): managed tree first, PATH kept as the fallback rung, None when a managed tree exists but cannot be healed (never silently a system copy).

npm also needs the managed dirs on PATH, not just an absolute path — npm's launcher runs under env node, and the sidecar shells out to node too. The npm runs and the sidecar spawn now use with_hermes_node_path().

An explicit PHOTON_NODE_BIN stays authoritative and is still validated.

Tests

tests/plugins/platforms/photon/test_managed_node_resolution.py — 11 tests. PATH is pinned empty in each one, so the managed rung decides the outcome rather than whatever the host has installed:

• check_requirements() accepts a managed Node; still False with no Node anywhere
• the sidecar spawns the managed interpreter
• reinstall and install-sidecar run the managed npm, with the managed dir on the child's PATH
• PHOTON_NODE_BIN still wins; a broken override is still a hard failure
• the env overlay keeps the caller's existing variables

scripts/run_tests.sh tests/plugins/platforms/photon/test_managed_node_resolution.py
=== Summary: 1 files, 11 tests passed, 0 failed ===

# without the fix
=== Summary: 1 files, 6 tests passed, 5 failed ===

Two existing tests were updated rather than worked around:

• test_inbound.py::test_check_requirements_without_node encoded the old "not on PATH → refuse" contract; it now stubs the managed resolver too, preserving its intent — no Node anywhere → refuse.
• test_npm_error_log_regression.py patched cli_mod.shutil.which, which cli.py no longer uses; the 7 patch lines now target the resolver. Assertions unchanged.

Broader run — tests/plugins/: 1077 passed, 9 failed, the same 9 that fail on a clean checkout. Baseline verified by stashing the change: 1066 passed, 9 failed — same set, zero new failures.

[teknium1]

Thanks for tracing the managed-runtime gap across the Photon adapter and CLI. The premise is confirmed on current main: plugins/platforms/photon/adapter.py:385, :406, :461, and :715 still rely on PATH-only resolution, while plugins/platforms/photon/cli.py:388 and :445 do the same. This conflicts with the established resolver contract in hermes_constants.py:653-679, which prefers the managed runtime and supplies its PATH to child processes.

The PR applies that existing mechanism at the affected sites, preserves the explicit PHOTON_NODE_BIN branch, and adds managed-path coverage for dependency installation and sidecar spawning. Remote main is only two unrelated commits beyond the PR base, so this should be mechanically salvageable.

Automated hermes-sweeper review.