Add cargo-watch hot reload for contract tests (cargo watch -x test)

[vjuliaife]

Description:
Rust contract developers currently must manually re-run cargo test after every code change, which interrupts flow and slows the red-green-refactor cycle. Adding cargo-watch support with a documented invocation (cargo watch -x test) provides instant feedback on file changes, keeping developers in their editor rather than their terminal. A convenience npm/Make target should wrap this so the command is easy to discover.

Acceptance Criteria:

• cargo-watch added as a dev-dependency in the Rust workspace Cargo.toml or documented as a required global install with an exact version pin
• A watch:contracts script added to the root package.json that runs cargo watch -x test from the contracts crate directory
• make watch-contracts target added to the Makefile (depends on issue Add Makefile with targets: dev, test, build, contract-deploy, db-migrate, db-reset, clean #352) that invokes the same command
• The watch command uses -w src/ to scope watching to source files only, ignoring target/ churn
• A .cargo/config.toml (or existing config) sets reasonable CARGO_INCREMENTAL=1 and parallel job limits for fast recompilation
• Documentation in the Rust crate README or CONTRIBUTING.md covers the hot-reload workflow and any platform-specific notes (e.g., inotify limits on Linux)
• CI does NOT use cargo watch — only the standard cargo test — ensuring no watch process blocks CI pipelines

Relevant Files:

• Cargo.toml — add cargo-watch dev dependency or document install requirement
• .cargo/config.toml — new or existing file for incremental build config
• package.json — add "watch:contracts" script
• Makefile — add watch-contracts target

[NickiM84]

@NickiM84 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello, I'm a fullStack developer with years of experience, I have worked on several projects, can I please work on this

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[devmocrea]

@devmocrea has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi maintainer, will love to work on this.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @devmocrea to this issue.

[drips-wave]

Congratulations, @devmocrea! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

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