Refactor NWC lud16 parsing to set initial value for lightning address

[ekzyis]

Description

This is a partial refactor of #2564.

Only partial, because the automatic switch to the lightning address if it has an initial value is still hard-coded in a useEffect:

stacker.news/wallets/client/components/form/hooks.js

Lines 59 to 64 in 6762fc0

	// we switch to the LN_ADDR protocol form if it exists and there's an initial value
	// else we just select the first protocol.
	const lnAddrProto = protocols.find(p => p.name === 'LN_ADDR')
	if (lnAddrForm?.initial.address && lnAddrProto) {
	setProtocol(lnAddrProto)
	} else {

Ideally, we would generally switch to the first protocol form that has an initial value.

Additional Context

#2575 will also use this code to set the identity public key from the mnemonic.

Checklist

Are your changes backward compatible? Please answer below:

yes

On a scale of 1-10 how well and how have you QA'd this change and any features it might affect? Please answer below:

8. Tested by pasting a Coinos NWC string and seeing the initial lightning address value set to the lud16 parameter. Also tested skipping NWC and SSR.

For frontend changes: Tested on mobile, light and dark mode? Please answer below:

n/a

Did you introduce any new environment variables? If so, call them out explicitly here:

no

Did you use AI for this? If so, how much did it assist you?

no

---

Note

Adds a generic populate for protocol fields and moves Lightning Address initial value derivation from NWC into the LN_ADDR protocol, with domain handling done via schema transform.

• Form logic:
  • Introduce field.populate support in useProtocolForm, using global form state to prefill values; remove NWC-specific parsing from hooks.js.
  • Normalize LUD-16 handling: strip domain from address in initial values and append via schema transform on submit.
• Protocols:
  • Extend ProtocolField type with populate callback.
  • LN_ADDR: add populate that reads lud16 from NWC URL (when present and domain-compatible) to prefill address.
• UI:
  • WalletProtocolFormField transforms now accept and ignore populate prop to avoid passing it to inputs.

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