Add the BK72xx flasher id to the hand-off protocol

[bdraco]

What does this implement/fix?

Adds bk-uart, the UART downloader of a Beken BK72xx, to the flasher ids of the web.esphome.io hand-off in the protocol's mirror here. Types and comments only: the test page still lists esp alone, so its handshake test is as it was.

Related issue or feature (if applicable):

• part of Flash LibreTiny BK72xx (bk72xx) from the browser over Web Serial device-builder-frontend#1795

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: Hand BK72xx firmware off to web.esphome.io device-builder-frontend#1935

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.index.json / definitions/components/*.json have not been hand-edited (regenerate via script/sync_components.py if a sync is needed).
• Architecture-level changes are reflected in docs/ARCHITECTURE.md and/or docs/API.md.

[bdraco]

@esphbot review

[codspeed]

Merging this PR will not alter performance

✅ 28 untouched benchmarks
⏩ 1 skipped benchmark¹

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_{Comparing handoff-flasher-ids (c8693ba) with main (c3bccb8)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.75%. Comparing base (c3bccb8) to head (c8693ba).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2862   +/-   ##
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  Coverage   99.75%   99.75%           
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  Files         296      296           
  Lines       25618    25618           
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  Hits        25556    25556           
  Misses         62       62           

Flag	Coverage Δ
py3.12	99.72% <ø> (ø)
py3.14	99.60% <ø> (ø)

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[esphbot]

PR Review — Add the BK72xx flasher id to the hand-off protocol

Merge-ready: this adds bk-uart to the hand-off flasher ids and changes nothing else. No issues found.

What the PR does well:

• bk-uart is added to the HandoffFlasher union in flasher/src/protocol.ts and matches the id used in the companion frontend PR Hand BK72xx firmware off to web.esphome.io device-builder-frontend#1935.
• Both doc comments (the per-flasher list and the note on how parts are laid out) now include BK72xx. They correctly class it with the other UF2-as-one-part-at-address-0 flashers, rtl-ambz2 and rp2-picoboot.
• The change is types and comments only, as the description says. flasher/src/main.ts:30 still sets FLASHERS to ["esp"], so the test page's handshake is unchanged.
• I searched the code for an exhaustive switch or Record<HandoffFlasher, …> over the union that the new member could break, and found none. The type is only used for flashers?: HandoffFlasher[], flasher?: HandoffFlasher and the FLASHERS constant.

No issues need attention.

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Checklist

• No hardcoded secrets
• Backward-compatible protocol change (additive union member only)
• No exhaustive switch/Record over HandoffFlasher broken by the new member
• Diff matches PR description (types and comments only)

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Automated review by Kōan (Claude) HEAD=c8693ba 13s

[esphbot]

Tip

No blocking issues found — ready to merge.

[Copilot]

Copilot review overview

🟢 Approval recommended

No unresolved review comments; the change is limited to protocol types and documentation.

Review effort: Lite
Findings: None

What changed in this PR

Adds the bk-uart flasher identifier to the BK72xx hand-off protocol.

Changes:

• Extends HandoffFlasher with bk-uart.
• Documents BK72xx UF2 hand-off behavior.

File	Summary
flasher/​src/​protocol.ts	Adds and documents the BK72xx flasher identifier.

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