investigate: capture raw NDEF bytes for app-written tags (#1098, #1106)

[wizzomafizzo]

Why

App-written NTAG213 tags don't launch on Core (#1098, #1106). Across the attached logs the failing
scans show a validly-formatted NTAG213 (valid Capability Container → variant=NTAG213,
hasNDEF=true) whose NDEF message is empty: messageNil=false with zero records, which is emitted
only when the NDEF TLV has a length byte of 0 (03 00). The record the app intended to write is not
where Core reads it.

go-pn532 already prints the exact bytes it reads from a tag (readNDEFHeader: user data = [...]) via
Debugf, but Core never wired that output anywhere, so the decisive bytes are absent from every log.
This PR captures them.

What

• New pkg/readers/pn532/debug.go: a zerologDebugWriter that forwards each go-pn532 debug line to
  log.Debug().Str("src","pn532"), installed once via sync.Once.
• pkg/readers/pn532/pn532.go: Open installs it when the existing debug_logging config is
  enabled. No new config key.
• Pairs with a new SetDebugWriter(io.Writer) hook in go-pn532 (see note below).

With debug_logging on, a failing app-written tag and a working Core-written tag can be scanned and
their byte dumps diffed to decide write-side vs read-side.

⚠️ Draft — remove local go-pn532 wiring before merge

This branch builds against a local sibling ../go-pn532 checkout because the SetDebugWriter
hook it calls is not yet in a released go-pn532. Two temporary bits must be undone before this can
merge:

1. go.mod — replace github.com/ZaparooProject/go-pn532 => ../go-pn532
2. scripts/tasks/docker.yml — the GOPN532_MOUNT var + its {{.GOPN532_MOUNT}} mount, which
   bind the sibling checkout into the build container so the replace resolves there too.

Before merge: land SetDebugWriter in go-pn532, cut a release, bump the go-pn532 version in go.mod,
and delete both items above.

Status

Parked pending on-device reproduction (a physically app-written failing tag scanned on the MiSTer
with debug_logging on). If the captured bytes show a genuine empty NDEF (03 00), the fix is
app-side (write read-back verification); if they show a valid record Core misreads, a read-side fix
lands in go-pn532.

An app-team write-up (read-back verification for #1098, hidden error toast for #1106) is kept locally
in docs/plans/nfc-app-write-verification.md (that directory is git-excluded, so it is not in this
PR).

[coderabbitai]

Important

Review skipped

Draft detected.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 7e46e772-147c-42a0-bd41-eb920599ae2d

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch investigate/nfc-write-1098-1106

---

_{Comment @coderabbitai help to get the list of available commands.}