Implement ProfilerSession with flame-graph-compatible timing output

[Kingsman-99]

Overview

Build out the ProfilerSession class to capture real timings for all SDK operations and produce output compatible with the speedscope flame graph viewer (JSON format). This is essential for diagnosing SDK performance bottlenecks in production.

Requirements

• ProfilerSession wraps a StellarSplitClient and records timing for every method call
• session.start() / session.stop() controls recording
• session.report(): SpeedscopeProfile returns a flame-graph-compatible JSON object (speedscope format v0.6)
• session.exportJSON(path: string): void writes the report to a file
• Tracks: method name, start time (ms), duration (ms), success/failure, nested RPC call timings
• Write tests asserting the report structure matches the speedscope schema (validated with ajv)
• Include a runnable example script (examples/profile-session.ts)

Acceptance Criteria

• ProfilerSession captures all SDK method timings
• Output matches speedscope v0.6 JSON schema
• exportJSON writes a valid file
• Example script runs end-to-end against a mock RPC
• npm test passes with zero failures
• TypeScript compiles with zero errors
• ESLint passes with zero errors

Definition of Done

All CI checks must pass before the PR is reviewed.

[nurudeenheroic]

Hello! I've reviewed the issue and can implement an efficient fix.

[Tobi-8]

Please maintainer assign me to this issue
I have the knowledge and skill to complete this task

[Eromosele0110]

i will like to fix this

[grantfox-oss]

🦊 GrantFox — @Eromosele0110 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #425)
2. Your PR will be reviewed by the Stellar-split maintainers

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