Fix TOML rendering crash on float config values

[derekwisong]

Problem

pyagent-config init crashed with TypeError: unsupported toml value: 0.3:

File "pyagent/config.py", line 236, in _render_toml_value
    raise TypeError(f"unsupported toml value: {v!r}")
TypeError: unsupported toml value: 0.3

_render_toml_value handled bool, int, str, and list, but not float — so rendering the commented default template blew up on the 0.3 temperature default in DEFAULTS.

Fix

Add a float branch to _render_toml_value that emits repr(v).

Test plan

• pyagent-config init --force succeeds and writes the default config + seeds roles