fix(show): include gitlab_id on notes in issue/MR detail views

The show command's NoteDetail and MrNoteDetail structs were missing
gitlab_id, making individual notes unaddressable in robot mode output.
This was inconsistent with the notes list command which already exposed
gitlab_id. Without an identifier, agents consuming show output could
not construct GitLab web URLs or reference specific notes for follow-up
operations via glab.

Added gitlab_id to:
- NoteDetail / NoteDetailJson (issue discussions)
- MrNoteDetail / MrNoteDetailJson (MR discussions)
- Both SQL queries (shifted column indices accordingly)
- Both From<&T> conversion impls

Deliberately scoped to show command only — me/timeline/trace structs
were evaluated and intentionally left unchanged because they serve
different consumption patterns where note-level identity is not needed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/cli/commands/show/render.rs

@@ -398,6 +398,7 @@ pub struct DiscussionDetailJson {
 
 #[derive(Serialize)]
 pub struct NoteDetailJson {
+    pub gitlab_id: i64,
     pub author_username: String,
     pub body: String,
     pub created_at: String,
@@ -458,6 +459,7 @@ impl From<&DiscussionDetail> for DiscussionDetailJson {
 impl From<&NoteDetail> for NoteDetailJson {
     fn from(note: &NoteDetail) -> Self {
         Self {
+            gitlab_id: note.gitlab_id,
             author_username: note.author_username.clone(),
             body: note.body.clone(),
             created_at: ms_to_iso(note.created_at),
@@ -497,6 +499,7 @@ pub struct MrDiscussionDetailJson {
 
 #[derive(Serialize)]
 pub struct MrNoteDetailJson {
+    pub gitlab_id: i64,
     pub author_username: String,
     pub body: String,
     pub created_at: String,
@@ -542,6 +545,7 @@ impl From<&MrDiscussionDetail> for MrDiscussionDetailJson {
 impl From<&MrNoteDetail> for MrNoteDetailJson {
     fn from(note: &MrNoteDetail) -> Self {
         Self {
+            gitlab_id: note.gitlab_id,
             author_username: note.author_username.clone(),
             body: note.body.clone(),
             created_at: ms_to_iso(note.created_at),