cli/serviceability: rewrite location get to rfc-20 conforming pattern

[juan-malbeclabs]

RFC-20 implementation stack

This PR is part of a 9-PR chain delivering RFC-20: CLI standardization. Each PR's diff is only its own contribution; reviewers should consume them in order.

#	PR	Scope
1	#3753	doublezero-cli-core foundation crate + solana_l1_rpc_url
2	#3754	--solana-url + --log-verbose global flags + tracing init
3	#3755	CliContext built in main + centralized error rendering
4	#3756	rename doublezero_cli → doublezero-serviceability-cli
5	#3757	rewrite location get as the async + CliContext reference verb
6	#3758	docs/cli-standard.md + CLAUDE.md pointer
7	#3759	move per-resource subcommand wrappers into the module crate
8	#3760	add ServiceabilityCommand enum + async dispatcher
9	#3761	#[command(flatten)] + collapse binary dispatch

This PR: #3757 — position 5 of 9. Previous: #3756 · Next: #3758

---

Summary of Changes

• Migrates location get to the RFC-20 conforming verb pattern as the project's reference (smartcontract/cli/src/location/get.rs). GetLocationCliCommand::execute is now async fn, takes &CliContext as its first non-self argument, and emits a tracing::debug! event so -v surfaces what the verb is doing.
• Updates the verb's unit test to consume the shared doublezero_cli_core::testing::cli_context_default_for_tests() helper and exercise the new async signature via a small tokio current-thread runtime in the existing #[test]. Backend stays mocked through MockCliCommand (auto-generated by #[automock]).
• Updates the binary dispatch arms in client/doublezero and controlplane/doublezero-admin to .await the new method. The doublezero-admin binary gets a doublezero-cli-core dep plus a small CliContext build at startup (matching the doublezero binary's pattern) so the new verb is callable end-to-end.
• The verb's user-facing args, flags, table layout, and JSON schema are unchanged. Other location verbs (Create, Update, List, Delete) keep their current sync signatures and migrate opportunistically per RFC-20's grandfathering clause.

Diff Breakdown

Category	Files	Lines (+/-)	Net
Core logic	3	+43 / -11	+32
Tests	1	+14 / -3	+11
Config/build	2	+2 / -0	+2
Docs	1	+1 / -0	+1
Generated	1	+14 / -7	+7
Total	7	+74 / -21	+53

One verb migrated end-to-end (async + CliContext + tracing + shared test helper); two binaries updated to .await the new dispatch arm.

Key files (click to expand)

• smartcontract/cli/src/location/get.rs - converts execute to async fn (self, ctx, client, out), adds the tracing::debug! event, rewrites the unit test to use cli_context_default_for_tests() and a small tokio current-thread runtime around the awaited call.
• client/doublezero/src/main.rs - one-line change: LocationCommands::Get(args) => args.execute(&ctx, &client, &mut handle).await.
• controlplane/doublezero-admin/src/main.rs - same one-line dispatch change plus a CliContextBuilder::new().with_env(...).build()? block at startup so &ctx is available.
• controlplane/doublezero-admin/Cargo.toml, smartcontract/cli/Cargo.toml - add doublezero-cli-core and tracing deps respectively.

Testing Verification

• cargo test -p doublezero-serviceability-cli location::get passes (the rewritten test exercises pubkey lookup, code lookup, and the not-found error path through the async signature).
• make rust-test green workspace-wide.
• make rust-lint clean.
• doublezero location get --help shows the same --code and --json flags as before; behavior unchanged from the user's perspective.
• Targets jo/4-cli-rename-serviceability; the diff shown is only this PR's contribution.

[vihu]

doublezero-admin now constructs a CliContext, but it only seeds .with_env(env_for_ctx) and drops the explicit admin globals (--url, --ws, --program-id, --keypair) that are still passed into DZClient.

Today location get only uses ctx.env for a debug log, so this is not a current output regression. But this PR makes location get the reference RFC-20 pattern, and future migrated verbs are expected to read backend/signing inputs from CliContext. In doublezero-admin, that would make migrated verbs see default env-derived values instead of the actual overrides used by DZClient.

Can we either mirror the client/doublezero/src/main.rs context-building behavior here or hold off on passing a partial context from doublezero-admin until it carries the same resolved inputs?