feat: add gas diff, deploy execute, repl history, and inspect json

[CMI-James]

Description

Implemented the four requested CLI enhancements in one grouped change set: gas diff comparison for WASM builds, optional deploy auto-execute with Stellar CLI detection, persistent REPL history controls, and JSON export support for contract inspection outputs.

Closes #124
Closes #104
Closes #121
Closes #107

Changes proposed

What were you told to do?

Implement Issues #124, #104, #121, and #107 in one PR by updating gas, deploy/info, shell/repl, and contract/inspect/soroban/docs behavior.

What did I do?

Gas Diff Command

• Added starforge gas diff <OLD_WASM> <NEW_WASM> in src/commands/gas.rs.
• Reused src/utils/profiler.rs timings to profile old/new analysis steps and total duration.
• Printed side-by-side wasm size and estimated simulation cost deltas.

Deploy Execute + Stellar Detection

• Added --execute flag in src/commands/deploy.rs with dry-run default behavior retained.
• Added Stellar CLI PATH detection helper in src/commands/info.rs and surfaced status in starforge info.
• Executed stellar contract deploy only when --execute is set and CLI exists; otherwise raised a clear error.

REPL History Persistence

• Added configurable REPL history options in src/utils/repl.rs with persistence at ~/.starforge/repl_history.
• Added --no-history opt-out and --history-max-lines in src/commands/shell.rs.
• Enforced max history line trimming during load/save and session writes.

Inspect JSON Output + Docs

• Added --json support to starforge contract inspect in src/commands/contract.rs.
• Added serde serialization derives for inspect result structs in src/utils/soroban.rs.
• Updated API_REFERENCE.md with new flags/commands and JSON schema docs for inspect outputs.

Check List (Check all the applicable boxes)

• My code follows the code style of this project.
• This PR does not contain plagiarized content.
• The title and description of the PR is clear and explains the approach.
• I am making a pull request against the main branch (left side).
• My commit messages styles matches our requested structure.
• The implementation was reviewed and confirmed to work as intended.
• I am only making changes to files I was requested to.

Screenshots / Validation Evidence

• Ran formatting on touched Rust files with
  ustfmt.
• Attempted cargo test --quiet; current upstream branch fails due pre-existing unrelated compile issues:
  • src/utils/mod.rs references missing module emplate
  • src/utils/templates.rs has an unclosed delimiter
• Confirmed requested file diffs are isolated to issue scope.

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