feat(discussion): add comment command - #13620

Implement gh discussion comment for adding, editing, and deleting
comments and replies on discussions. Supports --body, --body-file,
--editor for input, --reply-to for threading, --edit and --delete
for modifying existing comments, with confirmation prompts.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…PI calls

Replace gh api graphql addDiscussionComment mutations in view and list
acceptance tests with gh discussion comment. Extract comment IDs via
a single view call with jq2env instead of multiple calls.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Cover add, reply, edit, delete flows including body-file input,
non-interactive delete requiring --yes, and deletion of both parent
comment and reply to avoid ghost entries.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add test for --delete without --yes in non-TTY mode and fix existing
delete tests to set isTTY: true for prompter-based confirmation.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add ParseDiscussionOrCommentArg to the shared package for parsing
discussion numbers, URLs, comment node IDs, and comment URLs
(with #discussioncomment-NNNNN fragments).

Add ResolveCommentNodeID to the client for constructing node IDs from
repository database ID and comment database ID via msgpack encoding.

Update the comment command to accept comment URLs as positional args
for reply, edit, and delete operations. Update the view command to
accept comment URLs in the --replies flag.

Add DiscussionID field to DiscussionComment for reply flow (fetches
the parent discussion ID from a comment).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…ests

Update comment acceptance test to use positional comment IDs instead of
--reply-to, and add URL-based add/edit/delete test cases. Update view
acceptance test to cover --replies with a comment URL.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Signed-off-by: Babak K. Shandiz <babakks@github.com>

…ment argument

Drop the --replies flag from gh discussion view and instead accept a
comment URL or comment node ID (DC_*) as the positional argument. A
discussion number, #number, or discussion URL behaves as before, while a
comment reference shows that comment and its replies.

Rework GetCommentReplies to be node-centric: it resolves the parent
discussion directly from the comment node, so it no longer needs the
discussion number or a repository ownership check. The method now takes a
host string instead of a full repository.

Also add a comment mode for --web that resolves and opens the comment URL,
and add godoc to the DiscussionClient interface methods.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

GetComment resolves a comment by its node ID, so it only needs the host
to select the GraphQL endpoint. Change its signature from a full
ghrepo.Interface to a host string and update all callers and tests
accordingly, mirroring GetCommentReplies.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…test

Replace --replies usage with a positional comment node ID or URL to match
the redesigned gh discussion view command.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…gument

In replies mode the --comments flag is meaningless, so reject the
combination with a flag error instead of silently ignoring it.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>