fix(lint): stop reporting lengths that can never truncate

[venugopalanvip]

v2 only. Two false positives in ValidateMaxLengthLinter, both the same shape: it measures a string that never reaches a screen against the limit for strings that do. I found them while working through the registry's audit backlog, where the real length warnings are the ones you want to see.

1. A hidden label cannot be truncated

_collect_long_labels measured every label, including fields the device never draws.

$ erc7730 lint registry/p2p/calldata-P2pSsvProxyFactory.json
🟠 Display label too long: `Referrer Config Basis Points` exceeds 20 characters
   and may be truncated on Ledger devices.

That field is "visible": "never". Descriptors routinely spell out hidden struct leaves in full — it is how a reader tells #._referrerConfig.basisPoints from #._clientConfig.basisPoints.

Two rules mean "never drawn" and are now skipped:

rule	drawn?	measured?
always	yes	yes
optional	when the wallet can	yes
unset	yes	yes
ifNotIn	when the value is not in the list	yes
never	no	no
mustMatch	no — checked, not shown	no

mustMatch is worth spelling out: it is a constraint the device enforces without displaying the field, which is exactly why convert_erc7730_v2_input_to_calldata already lets such a field omit its label —

# A mustMatch field is never displayed, so the descriptor is allowed to omit its label, but
# the FIELD struct still requires a NAME tag.

A linter that permits no label while warning about a long one contradicts the converter.

ifNotIn and optional are deliberately not skipped: both reach a screen at least some of the time.

2. {path} is template syntax, not displayed text

interpolatedIntent was measured as written, so the braces and the path inside them counted toward the 30-character limit. Neither is displayed, and the length of the value that replaces them is not knowable here — an amount may render as 1 ETH or as eighteen decimal places.

Measured across every descriptor in the clear-signing registry:

	count
interpolated intents longer than 30 chars as written	109
of those, whose literal text still exceeds 30	24
warnings produced by the template syntax alone	85

78% of these warnings are about characters that never reach a device. The clearest case:

Swap {execution.desc.amount} for at least {execution.desc.minReturnAmount} to recipient {execution.desc.dstReceiver}

116 characters as written, 33 of literal text. {execution.desc.minReturnAmount} alone is 32 characters of path.

A real one that stops warning — registry/lido/calldata-stETH-L2.json:

Send {sharesAmount} to {recipient}      34 as written, 9 displayed

Only the literal text is certain to reach the screen, so that is what is measured now. Over the limit on that alone means the intent truncates whatever the values render to — conservative, and it keeps all 24 genuine cases, including the two examples above.

Severity and scope

Both remain warnings; nothing changes an exit code. Neither touches intent, id, metadata or enum lengths, which are literal strings and were always measured correctly.

Tests

tests/v2/lint/test_lint_validate_max_length.py is new: all six visibility rules, a ResolvedFieldGroup case proving a hidden child does not hide its visible sibling's label, and the literal-length measure including a 32-character path inside a placeholder and a literal that is genuinely over.

Verified end to end: the two warnings quoted above are gone, a long label on a visible field still reports, and a literal-only intent over 30 still reports.

[venugopalanvip]

Added a second false positive from the same linter in 67d66b2, and retitled accordingly — it is the same shape as the first, so it seemed better as one review than a second PR touching the same method.

interpolatedIntent was measured as written, so {path} counted toward the 30-character limit. Across the registry, 109 interpolated intents exceed 30 characters as written and only 24 have literal text that still does — so 85 of those warnings are about braces and path text that never reach a device. {execution.desc.minReturnAmount} is 32 characters on its own.

Only the literal text is measured now. Over the limit on that alone means the intent truncates whatever the values render to, so the check stays conservative and keeps all 24 genuine cases.

Happy to split this back out if you would rather review them separately.