feat(cli, config): Accept comma-separated tool names

[JeanMertz]

--tool and --no-tool take several tool names in one flag, separated by commas, so a query that opens up three tools no longer needs three flags:

jp query -t cargo_check,cargo_test,fs_read_file "Does this compile?"

Space around a name is ignored, repeating the flag still works and composes with the comma form, and each name keeps its place in the left-to-right order that --no-tool --tool=write relies on. A bare --tool or --no-tool is unchanged: it still covers every configured tool.

A missing value is refused rather than guessed at, wherever a comma separates values. -t read,,write reports the stray comma instead of reading it as the bare flag and enabling everything, and a --cfg list does the same instead of quietly dropping the gap. Assigning nothing at all is untouched: conversation.labels.crate= still names no values and remains the way to clear a list, and a value that genuinely contains a comma is written with the JSON form, crate:="feat,exp".

The tool-use documentation is corrected alongside. It described --tool=false, --tool=true, and --tool=<name>, which are spellings of --tool-use and --no-tool-use; --tool=false asks for a tool named "false" and errors.

BREAKING CHANGE: A tool name cannot contain a comma

Configuring a tool whose name contains a comma is rejected when the configuration resolves, naming the offending key:

conversation.tools.read,write: a tool name cannot contain a comma,
because `--tool` and `--no-tool` read it as a separator between names

Rename the tool to clear the error.