Add FirmwareJob.source / source_label fields (7a-2a)

[bdraco]

What does this implement/fix?

First slice of the transparent install flow described in
issue #106 § Transparent install flow.
Makes the local-vs-remote-build distinction a first-class
field on FirmwareJob: the firmware queue's runner branches
on source to choose its pipeline (local subprocess vs
peer-link submit_job dispatch), and the install dialog reads
source_label to decide whether to render the
"Building on {receiver_label}" sub-line.

No synthetic-job wrapper. No event-stream bridge. One
FirmwareJob per build, the same JOB_* lifecycle events fire
either way, source is the only place LOCAL and REMOTE diverge
from a caller's perspective. The original design doc proposed a
synthetic-FirmwareJob + bridge construction to avoid changing
the install dialog's subscriber; that was extra ceremony for a
problem that doesn't exist (frontend ships lockstep with
backend, so adding a small consumer in the dialog when this PR
lands is one coordinated change). Arch.md catches up in a
separate docs PR.

What lands

New JobSource StrEnum in models/firmware.py:

• LOCAL — this dashboard's CPU compiled the artifacts
  (today's default; matches every job-row written before this
  PR).
• REMOTE — a paired receiver compiled the artifacts and
  this dashboard fetched them via download_artifacts.

New fields on FirmwareJob:

• source: JobSource = JobSource.LOCAL — the discriminator.
• source_pin_sha256: str = "" — machine-readable handle
  on the receiver that compiled this job, when
  source == REMOTE. Matches StoredPairing.pin_sha256.
  Load-bearing for restart recovery: a crash-recovered REMOTE
  job needs to know which receiver to route
  download_artifacts / cancel_job against, and the RAM-only
  _open_peer_links cache doesn't survive the restart. Same
  shape as 5c-2's receiver-side remote_peer (machine id, not
  display label) and for the same reason.
• source_label: str = "" — display string for the
  receiver-label when source == REMOTE. Mirrors
  StoredPairing.label at job-creation time; doesn't track
  later renames of the pairing label (snapshot semantics). The
  machine-readable handle lookups go through is
  source_pin_sha256; source_label is purely for rendering.

All three default to the LOCAL shape so an offloader upgrading
across this landing sees its prior on-disk job-rows
deserialise correctly.

Distinct from remote_peer / remote_job_id — those are
receiver-side fields filled by 5c-2. The new fields are the
offloader-side for the same delegation seen from the
dispatching dashboard. Both pairs end up set on opposite-side
FirmwareJob rows for a single transparent dispatch.

FirmwareJob.reset()'s "preserves identity" list extended
to include source / source_pin_sha256 / source_label /
remote_peer / remote_job_id. The remote_* omission was
already a latent bug for 5c-2 receivers (a crashed
receiver-side job losing remote_peer would strand the
rebuild from the offloader's correlation cache). Pinned with
a new test.

Test additions

• test_source_defaults_to_local — default value.
• test_remote_source_round_trips_through_serialisation —
  persistence contract: all three new fields keep their values
  across a dashboard restart.
• test_older_sidecar_without_source_field_loads_as_local —
  upgrade-from-pre-7a-2a path: hand-crafted minimal JSON
  without the new keys deserialises with default values
  rather than crashing.
• test_malformed_source_value_rejected_on_load — corrupt
  source: "intergalactic" raises on construction; doesn't
  silently land in code that branches on
  is JobSource.REMOTE.
• test_reset_preserves_dispatch_origin_fields — all five
  dispatch-origin fields survive FirmwareJob.reset().

ruff + mypy clean. 9 tests in tests/models/test_firmware_job.py.

What this PR does NOT do

• No caller integration. The runner's source-routing
  branch lands in 7a-2b (rename of the previous "event-stream
  bridge" slice; the synthetic framing is gone in the new
  plan) alongside firmware/install integration in 7a-3.
  Today nothing reads the new field; landing it standalone
  keeps the model / persistence layer reviewable ahead of
  the runner's larger blast radius.
• No frontend consumer. The install dialog's
  "Building on {receiver_label}" sub-line lands when 7a-3
  wires firmware/install through the scheduler; the
  frontend FirmwareJob mirror gets the new fields then.
  Lockstep deployment means this is one coordinated PR
  rather than two waves of compatibility work.

Related issue or feature:

• Implements 7a-2a of issue Remote build offload: discover and delegate compiles to another dashboard on the LAN #106's § Transparent install flow.
  The 7a-2b (runner source-routing), 7a-3 (firmware/install
  integration), and 7a-4 (cancel translation) slices layer on
  top of this model change.
• Follow-up arch.md PR drops the synthetic-job / event-stream-
  bridge framing for the first-class shape this PR introduces.

Types of changes

• Bugfix (non-breaking change which fixes an issue) — bugfix
• New feature (non-breaking change which adds functionality) — new-feature
• Enhancement to an existing feature — enhancement
• Breaking change (fix or feature that would cause existing functionality to not work as expected) — breaking-change
• Refactor (no behaviour change) — refactor
• Documentation only — docs
• Maintenance / chore — maintenance
• CI / workflow change — ci
• Dependencies bump — dependencies

Frontend coordination

• No frontend change needed
• Companion frontend PR: esphome/device-builder-dashboard-frontend#

Checklist

• The code change is tested and works locally.
• Pre-commit hooks pass (ruff, codespell, yaml/json/python checks).
• Tests have been added or updated under tests/ where applicable.
• components.json has not been hand-edited.
• Architecture-level changes are reflected in docs/ARCHITECTURE.md and/or docs/API.md — follow-up docs PR drops the synthetic-job framing this PR replaces.

[codspeed-hq]

Merging this PR will not alter performance

✅ 12 untouched benchmarks

---

_{Comparing 7a-2a-firmware-job-source-field (6751574) with main (2c97a87)}

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.12%. Comparing base (2c97a87) to head (6751574).

Additional details and impacted files

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Flag	Coverage Δ
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py3.14	99.12% <100.00%> (+<0.01%)	⬆️

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Files with missing lines	Coverage Δ
esphome_device_builder/models/firmware.py	100.00% <100.00%> (ø)

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[Copilot]

Pull request overview

Adds a FirmwareJob “origin” discriminator so the backend can represent locally-built vs remotely-delegated firmware artifacts as the transparent install flow is layered in, while remaining backwards-compatible with pre-existing persisted job sidecars.

Changes:

• Introduce JobSource (LOCAL / REMOTE) and add FirmwareJob.source + FirmwareJob.source_label with LOCAL-shaped defaults for backward-compatible deserialization.
• Extend FirmwareJob.reset()’s “preserves identity” contract to explicitly include dispatch-origin fields (source, source_label, remote_peer, remote_job_id).
• Add unit tests covering defaults, JSON round-trip persistence, upgrade-from-older-sidecar behavior, and reset preservation.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
esphome_device_builder/models/firmware.py	Adds JobSource enum and new FirmwareJob fields for local vs remote build provenance; updates reset identity contract docs.
tests/models/test_firmware_job.py	Adds tests that pin defaults, persistence/deserialization compatibility, and reset preservation for dispatch-origin fields.