Add --ledger to stellar keys fund

[fnando]

What

Add a --ledger flag to stellar keys fund that connects to an attached Ledger hardware wallet, derives the public key at m/44'/148'/N', and funds the resulting account via the configured Friendbot. N defaults to 0 and can be set with --hd-path N.

stellar keys fund --ledger
stellar keys fund --ledger --hd-path 1

fund now flattens public_key::Cmd directly (the temporary Args shape introduced in #2557 to keep --ledger off fund is removed — Cmd is the single shape used by both keys address and keys fund). The Account <X> funded on <network> status line uses the resolved public key for <X> only when no name was supplied; the existing message format is unchanged when funding a named identity.

--ledger is mutually exclusive with the positional identity name; if neither is provided, clap rejects the command. Errors from a missing/locked device or a closed Stellar app surface through the existing signer::ledger error chain. Friendbot errors propagate through network::Error exactly as they do today.

Verified end-to-end against a real Ledger device.

Closes #2555.

Why

Hardware wallets are a primary key-management option in the CLI, and funding a freshly-derived address on testnet/futurenet is a routine first step in any development workflow. Without --ledger on fund, Ledger users have to derive their address out-of-band and fund it via other means — inconsistent with every other key type, which can be funded directly.

Known limitations

• Nothing is persisted — there is no keys add --ledger yet, so each invocation re-derives from the device and --hd-path lives only on the current call.

[Copilot]

Pull request overview

Adds Ledger-backed address resolution to stellar keys fund by reusing the existing keys address argument shape, so funding can target a connected hardware wallet without requiring a named local identity.

Changes:

• Replaces keys fund’s custom address args with public_key::Cmd, enabling --ledger and optional --hd-path.
• Updates keys fund success output so unnamed Ledger funding prints the resolved public key instead of a missing identity name.
• Refreshes help/docs and parser tests for the new keys fund --ledger CLI shape.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
FULL_HELP_DOCS.md	Updates the documented keys fund usage and options to mention optional NAME and --ledger.
cmd/soroban-cli/src/commands/keys/public_key.rs	Removes the older shared Args wrapper so Cmd becomes the shared address-resolution shape.
cmd/soroban-cli/src/commands/keys/fund.rs	Switches keys fund to the shared address command args, adjusts the status label, and adds parser tests.

Comments suppressed due to low confidence (1)

FULL_HELP_DOCS.md:1176

• The help text is now inconsistent with the command parser: NAME is shown as optional in the usage line, but the argument description still says the default test identity is used when it is omitted. In the new parser, omitting both NAME and --ledger is rejected, so these docs will send users to a command that now fails.

**Usage:** `stellar keys fund [OPTIONS] [NAME]`

###### **Arguments:**

- `<NAME>` — Name of identity to lookup, default test identity used if not provided

[fnando]

Fixed the stale <NAME> description in FULL_HELP_DOCS.md in 8233638 — regenerated via cargo run --package doc-gen so it now matches the parser ("Required unless --ledger is provided"). The [NAME] being optional in the usage line is correct: --ledger satisfies the requirement.