docs(execenv): expose label/subscriber CLI + complete create/update flag list

The agent-facing CLAUDE.md/AGENTS.md injected by InjectRuntimeConfig was
missing every doorway to non-core issue properties:

- `multica issue label list/add/remove` — the only way to label a newly
  created issue from the agent. Without it, agents either give up
  ("no command for that, please add it manually") or hallucinate flag
  names like `multica issue create --label foo` and fail.
- `multica issue subscriber list/add/remove` — same story for the
  subscribe-on-behalf flow.
- `multica label list/create` — agents need to discover existing label
  ids before they can attach one (we don't auto-create labels here).
- `issue create` flag list dropped `--project`, `--due-date`,
  `--attachment` even though the CLI has supported them for a while.
- `issue update` flag list dropped `--status`, `--assignee`,
  `--project`, `--due-date`, `--parent`, leaving agents thinking they
  could only edit title/description/priority via update.

Also splits `issue status` from `issue update` in the doc so the agent
sees the shortcut, and notes the `issue create` body intentionally
does NOT accept labels/subscribers (use the post-create commands).

server/internal/daemon/execenv/runtime_config.go

@@ -72,6 +72,9 @@ func buildMetaSkillContent(provider string, ctx TaskContextForEnv) string {
 	b.WriteString("- `multica issue get <id> --output json` — Get full issue details (title, description, status, priority, assignee)\n")
 	b.WriteString("- `multica issue list [--status X] [--priority X] [--assignee X] [--limit N] [--offset N] --output json` — List issues in workspace (default limit: 50; JSON output includes `total`, `has_more` — use offset to paginate when `has_more` is true)\n")
 	b.WriteString("- `multica issue comment list <issue-id> [--limit N] [--offset N] [--since <RFC3339>] --output json` — List comments on an issue (supports pagination; includes id, parent_id for threading)\n")
+	b.WriteString("- `multica issue label list <issue-id> --output json` — List labels currently attached to an issue\n")
+	b.WriteString("- `multica issue subscriber list <issue-id> --output json` — List members/agents subscribed to an issue\n")
+	b.WriteString("- `multica label list --output json` — List all labels defined in the workspace (returns id + name + color)\n")
 	b.WriteString("- `multica workspace get --output json` — Get workspace details and context\n")
 	b.WriteString("- `multica workspace members [workspace-id] --output json` — List workspace members (user IDs, names, roles)\n")
 	b.WriteString("- `multica agent list --output json` — List agents in workspace\n")
@@ -84,9 +87,15 @@ func buildMetaSkillContent(provider string, ctx TaskContextForEnv) string {
 	b.WriteString("- `multica autopilot runs <id> [--limit N] --output json` — List execution history for an autopilot\n\n")
 
 	b.WriteString("### Write\n")
-	b.WriteString("- `multica issue create --title \"...\" [--description \"...\"] [--priority X] [--assignee X] [--parent <issue-id>] [--status X]` — Create a new issue\n")
-	b.WriteString("- `multica issue assign <id> --to <name>` — Assign an issue to a member or agent by name (use --unassign to remove assignee)\n")
-	b.WriteString("- `multica issue comment add <issue-id> --content \"...\" [--parent <comment-id>]` — Post a comment (use --parent to reply to a specific comment)\n")
+	b.WriteString("- `multica issue create --title \"...\" [--description \"...\"] [--priority X] [--status X] [--assignee X] [--parent <issue-id>] [--project <project-id>] [--due-date <RFC3339>] [--attachment <path>]` — Create a new issue. `--attachment` may be repeated to upload multiple files; labels and subscribers are not accepted here, attach them after create with the commands below.\n")
+	b.WriteString("- `multica issue update <id> [--title X] [--description X] [--priority X] [--status X] [--assignee X] [--parent <issue-id>] [--project <project-id>] [--due-date <RFC3339>]` — Update one or more issue fields in a single call. Use `--parent \"\"` to clear the parent.\n")
+	b.WriteString("- `multica issue status <id> <status>` — Shortcut for `issue update --status` when you only need to flip status (todo, in_progress, in_review, done, blocked, backlog, cancelled)\n")
+	b.WriteString("- `multica issue assign <id> --to <name>` — Assign an issue to a member or agent by name (use `--unassign` to remove assignee)\n")
+	b.WriteString("- `multica issue label add <issue-id> <label-id>` — Attach a label to an issue (look up the label id via `multica label list`)\n")
+	b.WriteString("- `multica issue label remove <issue-id> <label-id>` — Detach a label from an issue\n")
+	b.WriteString("- `multica issue subscriber add <issue-id> [--user <name>]` — Subscribe a member or agent to issue updates (defaults to the caller when `--user` is omitted)\n")
+	b.WriteString("- `multica issue subscriber remove <issue-id> [--user <name>]` — Unsubscribe a member or agent\n")
+	b.WriteString("- `multica issue comment add <issue-id> --content \"...\" [--parent <comment-id>] [--attachment <path>]` — Post a comment (use `--parent` to reply to a specific comment; `--attachment` may be repeated)\n")
 	b.WriteString("  - **For multi-line content (anything with line breaks, paragraphs, code blocks, backticks, or quotes), you MUST pipe via stdin** — bash does NOT expand `\\n` inside double quotes, so writing `--content \"para1\\n\\npara2\"` stores the literal 4-char sequence and the comment renders without line breaks. Use a HEREDOC instead:\n")
 	b.WriteString("\n")
 	b.WriteString("    ```\n")
@@ -99,8 +108,7 @@ func buildMetaSkillContent(provider string, ctx TaskContextForEnv) string {
 	b.WriteString("\n")
 	b.WriteString("  - The same rule applies to `--description` on `multica issue create` and `multica issue update` — use `--description-stdin` and pipe a HEREDOC for any multi-line description; the inline `--description \"...\"` form is for short single-line text only.\n")
 	b.WriteString("- `multica issue comment delete <comment-id>` — Delete a comment\n")
-	b.WriteString("- `multica issue status <id> <status>` — Update issue status (todo, in_progress, in_review, done, blocked)\n")
-	b.WriteString("- `multica issue update <id> [--title X] [--description X] [--priority X]` — Update issue fields\n")
+	b.WriteString("- `multica label create --name \"...\" --color \"#hex\"` — Define a new workspace label (use this only when the label you need does not exist yet; reuse existing labels via `multica label list` first)\n")
 	b.WriteString("- `multica autopilot create --title \"...\" --agent <name> --mode create_issue [--description \"...\"]` — Create an autopilot\n")
 	b.WriteString("- `multica autopilot update <id> [--title X] [--description X] [--status active|paused]` — Update an autopilot\n")
 	b.WriteString("- `multica autopilot trigger <id>` — Manually trigger an autopilot to run once\n")