sdk/geolocation: GO: add instruction builders, executor, and write client…

[ben-dz]

Resolves: #3011

Summary of Changes

• Add transaction executor with signing, submission, and finalization logic
• Add 7 instruction builders (InitProgramConfig, UpdateProgramConfig, CreateGeoProbe, UpdateGeoProbe, DeleteGeoProbe, AddParentDevice, RemoveParentDevice) with Borsh-serialized args and account meta derivation
• Expand Client with write methods and Signer() accessor; New() now accepts a signer parameter
• Expand RPCClient interface with transaction submission methods

Note: This PR builds on #3179 (read-only SDK). Base branch is bdz/doublezero-3011-read-only.

Diff Breakdown

Category	Files	Lines (+/-)	Net
Core logic	10	+883 / -12	+871
Tests	3	+940 / -6	+934
Scaffolding	2	+19 / -0	+19

~50/50 split between implementation and tests.

Key files (click to expand)

• smartcontract/sdk/go/geolocation/instruction_test.go — 551 lines of tests covering all 7 instruction builders (account metas, args serialization, PDA derivation)
• smartcontract/sdk/go/geolocation/executor_test.go — 383 lines testing transaction lifecycle (happy path, preflight skip, blockhash errors, send failures, finalization timeout/errors)
• smartcontract/sdk/go/geolocation/executor.go — transaction executor: blockhash fetch, signing, submission, polling-based finalization with configurable timeout
• smartcontract/sdk/go/geolocation/client.go — adds executor field, signer parameter to New(), 7 write methods, Signer() accessor
• smartcontract/sdk/go/geolocation/create_geo_probe.go — instruction builder with 6 account metas and Borsh-serialized args
• smartcontract/sdk/go/geolocation/update_geo_probe.go — instruction builder for geo probe updates
• smartcontract/sdk/go/geolocation/add_parent_device.go — instruction builder for adding parent devices to a geo probe
• smartcontract/sdk/go/geolocation/remove_parent_device.go — instruction builder for removing parent devices

Testing Verification

• All 44 unit tests pass (24 from read-only base + 20 new write-side tests)
• Instruction tests verify correct account meta ordering, signer/writable flags, PDA derivation, and Borsh-serialized discriminant+args for all 7 instructions
• Executor tests cover happy path finalization, SkipPreflight propagation, blockhash/send/finalization error paths, and timeout behavior