feat(docker): user-set vs runtime config + persist HJSON comments

[madejackson]

Config vs runtime values + HJSON comment persistence in the compose editor

This PR is the combined follow-up to the HJSON display work: it shows the user-set config (instead of the live runtime state) and preserves HJSON comments in the compose editor.

🧩 Dependencies (all required — merge these first, in any order)

This branch is stacked on the following PRs. Each is needed because the code here builds on types/behavior they introduce:

#	PR	Why it's required
#584	Display & edit JSON payloads as HJSON	HJSON infra (hjson.jsx, toHjson, parseJsonOrHjson) that the compose editor edits in
#585	store healthcheck durations as compose-style strings	DurationStr / FormatDuration used by the export/diff code
#579	end-to-end depends_on + network_mode	ContainerRefToName, depends_on label handling, network-mode ref resolution
#573	normalize volume field casing to lowercase	CosmosMount (lowercase volume fields) used by export.go
#567	add support for shm_size	ShmSize / ByteSize byte-size string handling
#495	Add Exec form to command/entrypoint	strslice.StrSlice exec/shell form for command/entrypoint

1️⃣ Show user-set vs image-default config

Currently the compose editor always shows the live Docker runtime state, mixing user-set values with image-Dockerfile defaults (ENV, CMD, EXPOSE, HEALTHCHECK, WORKDIR, USER) and Cosmos bookkeeping labels.

• ExportContainerRuntime: exports only explicitly-set settings by diffing ContainerInspect against ImageInspectWithRaw:
  • env: only entries not in the image env or with a different value
  • labels: only labels are hidden if they are inherited verbatim from the image. The only label prefix hidden unconditionally is cosmos.compose.* (the internal per-node HJSON comment labels — returned separately via the comments field, not as user config). All other labels — including other cosmos.* / cosmos-* bookkeeping (cosmos.stack, cosmos-stack, cosmos.stack.main, cosmos-stack-main, cosmos-network-name, …) and com.docker.compose.* — are kept. The internal com.docker.compose.depends_on label is still stripped (its data is exposed via the depends_on field).
  • command/entrypoint/workingdir/user/stopsignal/hostname/domainname/healthcheck: only when they differ from the image
  • runtime/shm_size: hidden when they equal the docker daemon's defaults (read from the daemon)
  • ports/volumes/networks/resources/restart/dns exported as-is (no image baseline)
  • falls back to full runtime export if the image is unavailable
• ExportContainerRoute: ?from=initial (default) = diff; ?from=runtime = full live state
• Frontend: compose-editor gets a themed "Show runtime values" switch that re-fetches; newService.jsx re-syncs the editor when the service prop changes; empty fields (ports: [], routes: null, etc.) hidden via omitempty.

2️⃣ Persist HJSON comments in cosmos.compose.* labels

Comments aren't representable in JSON, so the editor previously lost them on save.

• Client: extractComments() builds a node-path → comment map; injectComments() restores them; create() sends $$comments; export returns comments.
• Backend: src/docker/comments.go stores each comment as cosmos.compose.<path> label and reads them back; CreateServiceRoute extracts $$comments; ExportContainerRoute returns the map.

Notes

• Once all dependency PRs merge into unstable, GitHub will show only this PR's delta.
• Multi-service stacks keep per-service comments (paths namespaced, e.g. services.web.image).
• Backend + client build clean; docker test suite passes.
• fixes [BUG]: Updating Docker images (that uses a base image) seemingly doesn't update variables, when the base image does #246

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[madejackson]

Rebased this branch on top of the updated #584 (f60d7bc3) so the stack is honest: #584 now provides the HJSON infra (including the min-quote presentation + grammar), and this PR's single commit carries only the user-set-vs-runtime export + comment preservation on top. The final hjson.jsx here is byte-identical to what was previously shipped; the history is just cleaner.