#329 Add 'swamp issue comment' command for updating existing issues

Problem Statement

There is no way to add a comment to an existing Lab issue from the CLI. When filing follow-up information (e.g., confirming a fix, adding reproduction details, or closing as resolved), the only option is to create a new issue referencing the old one, which fragments the conversation.

Proposed Solution

Add swamp issue comment <number> that appends a comment to an existing Lab issue.

# Non-interactive
swamp issue comment 327 --body "Confirmed fixed in 20260511.160514.0-sha.9d03b09a" --json

# Interactive (opens $EDITOR)
swamp issue comment 327

# Close with comment
swamp issue comment 327 --body "Fixed in latest build" --close --json

CLI schema

swamp issue comment <number>
  -b, --body <body>         Comment text (skips editor)
  -x, --extension <name>    Route to extension's issue tracker
  --close                   Also close the issue
  --reopen                  Also reopen the issue
  --json                    Output in JSON format

Output shape

{
  "method": "lab",
  "issueNumber": 327,
  "commentId": 42,
  "action": "commented",
  "closed": true
}

Extension-scoped comments

For third-party extensions with a GitHub repository, route via gh issue comment:

swamp issue comment 58 --extension @webframp/aws-ops --body "Fixed in v2026.05.08.1"

Alternatives Considered

• Using the web UI — works but breaks the CLI-first workflow
• Filing a new issue referencing the old one — fragments conversation (what we do today)