feat: NotePing() allows for testing to see if a notecard is responding sans delays/retry

[rayozzie]

The new NotePing method issues an echo transaction without delays or retries so that one can quickly determine whether a notecard is connected and communicating successfully. This is used by the note-arduino notecard.ping() to do automatic baud rate recovery during init.

[zakoverflow]

Requesting changes.

The intent of a fast single-attempt connectivity probe for autobaud makes sense, but this PR currently changes the behavior of the normal transaction path in a way that breaks existing note-c architecture.

Blocking findings:

1. _noteTransactionShouldLock() now ignores reset failure for all normal transactions.

In n_request.c, the reset-required path changed from "attempt reset, abort if reset failed" to "call _Reset(), ignore the result, clear resetRequired, and continue." That is why CI is failing in NoteTransaction_test.cpp: the tests expect no _noteJSONTransaction() call after a failed reset, but the PR now proceeds into the transaction anyway.

This should not be fixed by changing those tests. The old behavior is the right contract for NoteTransaction(): if the transport is known to require reset/re-sync and reset fails, the library should not attempt the user request/command on a known-bad interface. If NotePing() needs to bypass reset state for autobaud probing, that exception should stay inside NotePing() only.

Suggested fix: restore the previous reset failure handling in _noteTransactionShouldLock(), and keep the "do not honor resetRequired" behavior local to NotePing().

2. NotePing() bypasses the existing I2C locking discipline while draining input.

_notePingDrainInput() calls _I2CReceive() directly. Existing I2C transaction/reset flows lock around I2C operations via _i2cNoteTransaction(), _i2cNoteReset(), or the I2C mutex helpers. This direct receive path can race with other I2C users and does not fit the existing transport abstraction.

Suggested fix: either use an existing locked abstraction for the drain or explicitly take/release the I2C mutex around this drain path.

3. API naming/docs need to reflect that this is a transport probe, not a general health check.

NotePing() is acceptable if we want a simple public name, but the implementation does a very specific thing: it sends one echo, skips reset, skips CRC, skips retries, suppresses normal transaction logs, uses a short fixed timeout, and drains residual serial/I2C input. That is closer to a transport/autobaud probe than a normal "is the Notecard healthy?" API.

I would consider NoteProbe() or NoteProbeConnection() if this is primarily for autobaud/transport detection. If we keep NotePing(), the docs should explicitly say it is a single-attempt transport probe and not a substitute for the normal request path.

Test notes:

• The unit-test failures are explained by finding #1: NoteTransaction_test.cpp reset-failure sections now see _noteJSONTransaction() called after failed reset.
• The failing notecard-binary-test appears unrelated to this PR. The job failed before firmware tests ran because the Notestation reservation client exited with Connect call failed ('100.87.163.107', 65432).

I would be comfortable with this API after the normal transaction reset semantics are restored, the I2C drain follows the established locking model, and focused tests are added for NotePing() success/failure/no-retry/resetRequired/drain behavior.

[zakoverflow]

I prepared the requested follow-up commit, but I cannot push directly to this PR branch: GitHub rejected zakoverflow pushing to blues:ray/autobaud with 403.

I opened the commit as a companion PR targeting this branch:

#241

That PR:

• restores the original _noteTransactionShouldLock() reset-or-fail behavior, removing the reset-policy change from this PR
• adds focused NotePing() unit coverage for success, nonce mismatch, error response, invalid JSON, transaction error, missing response, no retry, no reset when resetRequired is set, transaction-start failure cleanup, no CRC, 500 ms timeout, newline termination, and serial drain before transmit

Verification in the note-c CI container:

• NotePing_test: 30 assertions passed
• NoteTransaction_test: 124 assertions passed