The Photon iMessage sidecar needs node_modules under
plugins/platforms/photon/sidecar/, but hosted/managed images keep the
whole install tree under an immutable /opt/hermes — every install and
self-heal path (setup CLI, stale-deps reinstall, cold install) died on
EROFS, and hosted users have no shell to work around it.
Three-layer fix, mirroring the WhatsApp bridge resolver pattern:
1. Bake the deps into the image. The Dockerfile now runs npm ci for the
sidecar in the layer-cached dependency stage (deterministic installs
from the committed lockfile; the postinstall spectrum-ts patch runs
at build time). Hosted happy path needs no runtime install at all.
2. New sidecar_paths.resolve_sidecar_dir() decides where the sidecar
runs from: PHOTON_SIDECAR_DIR override > writable source dir (dev
installs, unchanged) > read-only dir with baked fresh deps (managed
image) > mirror to $HERMES_HOME/photon/sidecar (writable data
volume) when deps are missing or stale in a read-only tree. The
mirror refreshes changed source files on image updates while
keeping node_modules, so the existing lockfile-staleness self-heal
works there.
3. connect() can now cold-install: _start_sidecar() runs the bounded
npm ci bootstrap when node_modules is missing instead of raising
immediately, and check_requirements() reports available when a
self-install is possible (npm present + writable resolved dir) so
the gateway actually creates the adapter on hosted instances. A
failed bootstrap still raises the actionable error, which connect()
surfaces as the retryable SIDECAR_FAILED fatal state on the
dashboard.
Tests: resolver decision table (env override, in-place, mirror,
refresh, fail-open), cold-install lifecycle paths, and a Dockerfile
contract test guarding the baked-deps + no-chown invariants.
Fixes NS-606.
