chore(dashboard): fix bugs found in dashboard review - #135

Fixes a batch of bugs found during a review of the dashboard web app. Each fix was developed in an isolated worktree and merged together; the combined branch builds, vets, and is gofmt-clean.

Fixes

Critical

• Pipeline "Create" page crash — the traces panel dereferenced p.Pipeline.Id unconditionally; on /pipelines/create Pipeline is nil, panicking mid-render. The panel is now guarded with {% if p.Pipeline != nil %}. (views/pipelineEditPage.qtpl)

High

• Device list pagination dropped the sensor-group filter — createSensorGroup/deleteSensorGroup passed a bare cursor where a URL was expected (breaking infinite scroll), and getDevicesTable/deviceListPage omitted sensor_group from the next-page URL (page 2+ returned all devices). All four spots now build full …?sensor_group=&cursor= URLs (delete correctly omits the filter). (routes/overview.go)
• Datastream websocket missing returns — bad start/end params wrote an HTTP error then still tried to upgrade the socket on a committed response. Added return after each parse error. (routes/overview.go)

Medium

• updatePipeline error handling — read resp.Body when resp could be nil, fell through to a nil-deref status check, and had an unreachable errors.As branch. Rewritten to be nil-safe and return after surfacing the error. Superseded by the shared error helper in the review follow-up below. (routes/pipelines.go)
• Trace timeline panic — trace.WorkerTimes[j] could index out of range when the API returns fewer times than workers. Added a bounds guard. (routes/ingress.go)
• Worker description couldn't be cleared — empty form values were skipped; description is now sent whenever the form contains the field (refined in the review follow-up below). (routes/workers.go)
• Create-worker ignored the Enabled toggle — createWorker now reads state and sets it. (routes/workers.go)

Low / robustness

• Added middleware.Recoverer so handler/template panics return a clean 500 instead of dropping the connection. (main.go)
• Fixed formatSince copy ("About 1 hour ago" / "About 1 minute ago") and removed a duplicated branch. (routes/ingress.go)
• Closed websocket frame writers per-iteration instead of defer-ing in a loop. (routes/overview.go)
• Removed stray fmt.Print* debug statements. (workers.go, pipelines.go, main.go)

Review follow-ups (4249155)

A second review pass on this branch surfaced seven more findings, all fixed:

• Pipeline create/update failures now surface the API's error — new shared handleAPIClientError helper unwraps api.GenericOpenAPIError, shows the API's message in the snackbar, and writes a real error status (previously update fell through to a generic snackbar with HTTP 200, so htmx treated failed saves as successful; create returned a raw HTTP error). The unreachable errors.As(*web.APIError) branch and the dead StatusCode != StatusCreated block are removed. (routes/pipelines.go)
• updateWorker description PATCH semantics — the field is only sent when present in the form (presence check via r.Form), so an omitted key no longer erases the stored description while an explicitly emptied textarea still clears it, matching the server's nil=keep / ""=clear contract. (routes/workers.go)
• CSRF rejections are logged again — the nosurf failure handler bypasses the chi logger, so it now logs nosurf.Reason with method and path, and returns 400 instead of a silent 200. (main.go)
• Deduplicated next-page URL construction — one devicesTableNextPage(next, sensorGroupID) helper replaces four inline copies that sourced sensor_group three different ways. (routes/overview.go)
• Deduplicated worker state mapping — formState(r) replaces the duplicated checkbox switch in createWorker/updateWorker. (routes/workers.go)
• formatSince pluralization — extracted an about(n, unit) helper; "About 1 second ago" now renders correctly and negative durations from clock skew clamp to zero. (routes/ingress.go)

Verification

go build ./services/dashboard/..., go vet ./services/dashboard/..., and gofmt -l all clean.

Not included (cosmetic / larger calls)

Worker name field styled to look disabled but editable; empty 200 on non-HTMX table endpoints; external CDN dependencies; unescaped server data in inline <script> strings; dead Trace.PipelineName.

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