Make contract invoke auto-convert values when type is string.

[fnando]

What

Before:

# Before
$ stellar contract invoke --id hello-world --send yes -- hello --to 5
❌ error: Failed to parse argument 'to': invalid type: integer `5`, expected string or map

Context: Expected type string, but received: '5'

After:

$ stellar contract invoke --id hello-world --send yes -- hello --to 5
ℹ️ Simulating transaction…
ℹ️ Signing transaction: 5e9c45b7a4003f110f10c703e4033a890566ba30d15f7a1644294b3abbe02f92
🌎 Sending transaction…
✅ Transaction submitted successfully!
📅 CBO5PAY52ACVZMWQFLJV3L7FD67LFHC6QA6WFRXS2IHRBVMDNLZ6557D - Success - Event: [{"string":"hello"}] = {"string":"5"}
["Hello","5"]

[fnando] in Projects/stellar/hello on  main !? +471 -139  v22.15.0  v1.93.0  25.1.0
$ stellar contract invoke --id hello-world --send yes -- hello --to '"5"'
ℹ️ Simulating transaction…
ℹ️ Signing transaction: f901a379dd7164c00475db8c3ac579645f7a27336180e4cfd289a767b7188b0a
🌎 Sending transaction…
✅ Transaction submitted successfully!
📅 CBO5PAY52ACVZMWQFLJV3L7FD67LFHC6QA6WFRXS2IHRBVMDNLZ6557D - Success - Event: [{"string":"hello"}] = {"string":"5"}
["Hello","5"]

Why

Fix #2334 and #2421.

Known limitations

N/A

[Copilot]

Pull request overview

This PR improves stellar contract invoke argument parsing by coercing non-quoted numeric inputs into String contract parameters, aligning CLI behavior with the contract function’s declared type (fixes #2334).

Changes:

• Coerce non-string JSON primitives into Value::String when the expected ScType is String.
• Add unit tests covering String parsing from numeric, boolean, bare-word, and JSON-quoted inputs.