docs(rest/python): fix merchant server quick start

[FanouZeng-TT]

Description

The Flower Shop client README's Merchant Server quick start is formatted as a multi-line inline code span beginning with:

bash uv run server.py

uv is an executable binary, so bash uv ... asks Bash to interpret that binary as a shell script and exits with code 126 (cannot execute binary file). The surrounding multi-line inline code is also difficult to copy as a command.

Fix: use the same direct uv run server.py invocation documented by the server README and format the existing arguments as a shell code block.

Category (Required)

• Core Protocol: Changes to the base communication layer, global context, or breaking refactors. (Requires Technical Council approval)
• Governance/Contributing: Updates to GOVERNANCE.md, CONTRIBUTING.md, or CODEOWNERS. (Requires Governance Council approval)
• Capability: New schemas (Discovery, Cart, etc.) or extensions. (Requires Maintainer approval)
• Documentation: Updates to README, or documentations regarding schema or capabilities. (Requires Maintainer approval)
• Infrastructure: CI/CD, Linters, or build scripts. (Requires DevOps Maintainer approval)
• Maintenance: Version bumps, lockfile updates, or minor bug fixes. (Requires DevOps Maintainer approval)
• SDK: Language-specific SDK updates and releases. (Requires DevOps Maintainer approval)
• Samples / Conformance: Maintaining samples and the conformance suite. (Requires Maintainer approval)
• UCP Schema: Changes to the ucp-schema tool (resolver, linter, validator). (Requires Maintainer approval)
• Community Health (.github): Updates to templates, workflows, or org-level configs. (Requires DevOps Maintainer approval)

Related Issues

N/A

Checklist

• I have followed the Contributing Guide (including Conventional Commits title requirements and ! for breaking changes).
• I have updated the documentation (if applicable).
• My changes pass all local linting and formatting checks.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• (For Core/Capability) I have included/updated the relevant JSON schemas.
• I have regenerated Python Pydantic models by running generate_models.sh under python_sdk.

Screenshots / Logs (if applicable)

Extracted the updated command from the README and verified its shell syntax. With the documented database initialized, the command starts the Merchant Server and /.well-known/ucp returns the 2026-04-08 profile. The repository-wide pre-commit suite and git diff --check also pass.