fix(agents): coerce a non-string description in TOML command rendering

[jawwad-ali]

Problem

CommandRegistrar.render_toml_command passes the raw frontmatter description straight into _render_basic_toml_string, which iterates the value and calls ord() on each character. Frontmatter comes from yaml.safe_load, so description can be any YAML type:

description='ok string'  ->  description = "ok string"
description=None         ->  TypeError: 'NoneType' object is not iterable
description=42           ->  TypeError: 'int' object is not iterable
description=True         ->  TypeError: 'bool' object is not iterable
description=['a','b']    ->  description = "ab"        <- silently WRONG value

description: with no value is the easy one to hit — plain YAML for an empty field.

Format-branch asymmetry

This is the only renderer reached from register_commands' format branches that does not normalise description:

branch	handling
render_yaml_command (same class, ~70 lines below)	already coerces: if not isinstance(description, str): description = str(description) if description is not None else ""
render_markdown_command	goes through yaml.dump, which handles any type
built-in gemini/tabnine template path (TomlIntegration._extract_description)	returns "" for a non-str
render_toml_command	no guard

So extension/preset commands rendered for the two TOML agents were the only ones affected.

Fix

Apply the same coercion the sibling already uses. After:

None       -> description = ""
42         -> description = "42"
True       -> description = "True"
['a','b']  -> description = "['a', 'b']"
1.5        -> description = "1.5"

Each still parses as valid TOML (asserted via tomllib.loads). String descriptions are untouched, so existing output is byte-identical.

Verification

• test_render_toml_command_coerces_non_string_description — 4 parametrized types, asserted through tomllib.loads: all 4 fail before this change, pass after.
• The 7 pre-existing test_render_toml_command_* tests (embedded triple quotes, multiline, control characters, backslashes, trailing backslash) all still pass — 11 passed together.
• uvx ruff@0.15.0 check src tests clean.

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AI-assisted: authored with Claude Code. I reproduced each failure mode through the real renderer on main, including the silent ['a','b'] -> "ab" mangling, and confirmed the sibling YAML branch already handled all three before mirroring it.