tool_paramhlp: --proto only supports one modifier

[bagder]

1 - clarify the documentation

2 - make curl exit with an error for unknown protocols to make users
better notice when they get it wrong

Verified in test 322

[Copilot]

Pull request overview

This PR updates --proto handling to better communicate misuse: documentation clarifies modifier usage and the CLI now treats unknown protocol tokens as a fatal parameter error (validated with a new regression test).

Changes:

• Add test322 to ensure --proto with multiple modifiers fails with exit code 2 and expected stderr.
• Change --proto parsing to error out (not just warn) on unrecognized protocol tokens.
• Clarify --proto documentation to indicate a single modifier (rather than “zero or more”).

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
tests/data/test322	New regression test for --proto with multiple modifiers (expects PARAM_BAD_USE).
tests/data/Makefile.am	Registers test322 in the test list.
src/tool_paramhlp.c	Makes unknown protocol tokens in --proto a hard error (PARAM_BAD_USE).
docs/cmdline-opts/proto.md	Adjusts wording about modifier count (but still needs a follow-up doc fix—see comment).

Suppressed comments (1)

docs/cmdline-opts/proto.md:25

• The text later in this document still says unknown/disabled protocols only produce a warning, but the implementation now errors out and exits (see updated proto2num behavior and test322 expectations). Update the documentation to match the new fatal-error behavior.

prefixed by a modifier. Available modifiers are:

## +
Permit this protocol in addition to protocols already permitted (this is
the default if no modifier is used).

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[testclutch]

Analysis of PR #22687 at ac295499:

Test 322 failed, which has NOT been flaky recently, so there could be a real issue in this PR. Note that this test has failed in 12 different CI jobs (the link just goes to one of them).

Generated by Testclutch