Improve --custom flag usability for non-interactive use

[steven-range]

Problem: --custom is broken for non-interactive use (CI, scripts, agents):

• Help text just says "Edit custom fields" — no format guidance
• Passing the display name ("Story point estimate=1") or API key (customfield_10016=1) both silently fail
• The validation warning says "not configured" but doesn't tell you what the correct format is or list valid field names
• Piping input without --no-input segfaults in the survey library

Required format (undocumented): lower-kebab-case of the configured field name, e.g. story-point-estimate=1

Proposed changes:

1. Help text on --custom flag shows the expected format with examples
2. Validation warning suggests similar field names using token matching, substring matching, and API key → name resolution
3. Covers issue edit, issue create, and epic create

No behavior changes — just better help text and actionable error messages.

I have a local build that does these, adds a bit of help text, and includes a call to a new suggestCustomFields method that matches as described. It's worked to allow my agent to find custom fields on our JIRA boards, so I'd like to contribute it back.

[YAMLcase]

funny, I was just struggling with this trying to feed a name with parenthesis. Save me a dive into the source code: where did you find the kebab-case bit?

[steven-range]

Validation — internal/cmdcommon/create.go:252 — builds the kebab identifier:

identifier := strings.ReplaceAll(strings.ToLower(strings.TrimSpace(configured.Name)), " ", "-")

You'd have to use something like custom-field-(parens)=3, I think.

API request construction — pkg/jira/edit.go:370 and pkg/jira/create.go — same transform.