remove: deprecated show command from CLI

The `show` command (`lore show issue 42` / `lore show mr 99`) was
deprecated in favor of the unified entity commands (`lore issues 42` /
`lore mrs 99`). This commit fully removes the command entry point:

- Remove `Commands::Show` variant from clap CLI definition
- Remove `Commands::Show` match arm and deprecation warning in main.rs
- Remove `handle_show_compat()` forwarding function from robot_docs.rs
- Remove "show" from autocorrect known-commands and flags tables
- Rename response schema keys from "show" to "detail" in robot-docs
- Update command descriptions from "List or show" to "List ... or
  view detail with <IID>"

The underlying detail-view module (`src/cli/commands/show/`) is
preserved — its types (IssueDetail, MrDetail) and query/render
functions are still used by `handle_issues` and `handle_mrs` when
an IID argument is provided.

src/cli/autocorrect.rs

@@ -290,7 +290,6 @@ const COMMAND_FLAGS: &[(&str, &[&str])] = &[
             "--source-branch",
         ],
     ),
-    ("show", &["--project"]),
     ("reset", &["--yes"]),
     (
         "me",
@@ -396,7 +395,6 @@ const CANONICAL_SUBCOMMANDS: &[&str] = &[
     "backup",
     "reset",
     "list",
-    "show",
     "auth-test",
     "sync-status",
 ];