feat: projects command — find the project IDs the config is missing

Reading gizmo_id during normalization fixed attribution, but it cannot
answer "which projects am I missing?": normalization only runs on
conversations being exported, and a normal run skips everything already
cached. Discovering the gaps would have meant --force re-exporting the
whole archive.

`ai-chat-exporter projects` does it directly. It lists conversations,
collects the g-p- ids they belong to, resolves display names, and prints a
table marking which are absent from .env plus a paste-ready
CHATGPT_PROJECT_IDS line. --write applies it; --deep falls back to one
detail request per conversation when the listing does not carry gizmo_id
(unverified which shape this account returns, so the command reports which
path it took rather than assuming).

This matters beyond tidiness: attribution is now self-correcting, but the
listing pass still needs the ids. Conversations that live only inside a
project never appear in the default listing, so an unlisted project's chats
are not merely misfiled — they are never fetched.

6 CLI tests: reporting, the already-configured case, the g-p- guard, --deep,
the hint when --deep is needed, and --write. 324 pass.

src/main.py

@@ -332,6 +332,143 @@ def doctor(ctx: click.Context) -> None:
         sys.exit(1)
 
 
+@cli.command()
+@click.option(
+    "--deep",
+    is_flag=True,
+    help=(
+        "Fetch each conversation's detail when the listing does not name its "
+        "project. Slow (one request per conversation) but complete."
+    ),
+)
+@click.option("--write", is_flag=True, help="Write the discovered IDs to .env.")
+@click.pass_context
+def projects(ctx: click.Context, deep: bool, write: bool) -> None:
+    """Discover ChatGPT project IDs, including ones missing from your config.
+
+    CHATGPT_PROJECT_IDS has to be maintained by hand, and a project missing
+    from it is invisible to the listing pass: conversations that live only
+    inside that project are never fetched at all. This finds the projects your
+    account actually uses and prints a paste-ready line.
+    """
+    cfg = _load_config_or_exit(ctx.obj["debug"])
+    if not cfg.chatgpt_session_token:
+        console.print("[red]CHATGPT_SESSION_TOKEN is not set — run 'ai-chat-exporter auth'.[/red]")
+        sys.exit(1)
+
+    from src.providers.chatgpt import ChatGPTProvider
+
+    try:
+        prov = ChatGPTProvider(
+            session_token=cfg.chatgpt_session_token,
+            session_token_1=cfg.chatgpt_session_token_1,
+            project_ids=cfg.chatgpt_project_ids,
+        )
+    except ProviderError as e:
+        _handle_provider_error(e, ctx.obj["debug"])
+        sys.exit(1)
+
+    configured = list(cfg.chatgpt_project_ids)
+    console.print(f"\n[bold cyan][CHATGPT][/bold cyan] {len(configured)} project ID(s) configured")
+    console.print("Listing conversations…")
+
+    try:
+        summaries = prov.fetch_all_conversations(since=None)
+    except ProviderError as e:
+        _handle_provider_error(e, ctx.obj["debug"])
+        sys.exit(1)
+
+    found: dict[str, str] = {}
+    missing_gizmo: list[dict] = []
+    for conv in summaries:
+        gizmo_id = conv.get("gizmo_id")
+        if gizmo_id and str(gizmo_id).startswith("g-p-"):
+            found.setdefault(gizmo_id, "")
+        elif gizmo_id is None:
+            missing_gizmo.append(conv)
+
+    if found:
+        console.print(
+            f"  [dim]The listing names a project on {len(summaries) - len(missing_gizmo)} "
+            f"conversation(s) — no detail fetches needed.[/dim]"
+        )
+    else:
+        console.print(
+            "  [yellow]The listing does not carry gizmo_id, so projects can only be "
+            "read from conversation details.[/yellow]"
+        )
+
+    if deep and missing_gizmo:
+        console.print(
+            f"  Fetching detail for {len(missing_gizmo)} conversation(s) "
+            f"(~{len(missing_gizmo) * cfg.request_delay / 60:.0f} min at "
+            f"{cfg.request_delay}s pacing)…"
+        )
+        from rich.progress import (
+            BarColumn, Progress, SpinnerColumn, TaskProgressColumn, TextColumn,
+        )
+
+        with Progress(
+            SpinnerColumn(),
+            TextColumn("[progress.description]{task.description}"),
+            BarColumn(),
+            TaskProgressColumn(),
+            console=console,
+        ) as progress:
+            task = progress.add_task("Scanning…", total=len(missing_gizmo))
+            for conv in missing_gizmo:
+                conv_id = conv.get("id") or conv.get("conversation_id")
+                if conv_id:
+                    try:
+                        raw = prov.get_conversation(conv_id)
+                        gizmo_id = raw.get("gizmo_id")
+                        if gizmo_id and str(gizmo_id).startswith("g-p-"):
+                            found.setdefault(gizmo_id, "")
+                    except ProviderError:
+                        pass
+                progress.advance(task)
+    elif missing_gizmo and not found:
+        console.print(
+            f"  [dim]Re-run with --deep to read {len(missing_gizmo)} conversation "
+            "detail(s). Nothing to report without it.[/dim]"
+        )
+
+    for gizmo_id in list(found) + [p for p in configured if p not in found]:
+        found[gizmo_id] = prov._fetch_project_name(gizmo_id)
+
+    table = Table(title="ChatGPT Projects", show_header=True)
+    table.add_column("Project", style="cyan")
+    table.add_column("ID", style="dim")
+    table.add_column("In .env")
+    for gizmo_id, name in sorted(found.items(), key=lambda kv: kv[1].lower()):
+        in_env = gizmo_id in configured
+        table.add_row(
+            name,
+            gizmo_id,
+            "[green]yes[/green]" if in_env else "[yellow]NO — add it[/yellow]",
+        )
+    console.print(table)
+
+    new_ids = [g for g in found if g not in configured]
+    if not new_ids:
+        console.print("[green]Every project found is already configured.[/green]")
+        return
+
+    combined = configured + new_ids
+    line = "CHATGPT_PROJECT_IDS=" + ",".join(combined)
+    console.print(
+        f"\n[bold]{len(new_ids)} project(s) missing from your config.[/bold] "
+        "Conversations that live only inside them are not being exported."
+    )
+    console.print("\n[dim]Paste into .env:[/dim]")
+    console.print(line)
+
+    if write:
+        _set_env_key("CHATGPT_PROJECT_IDS", ",".join(combined))
+    else:
+        console.print("\n[dim]Or re-run with --write to update .env directly.[/dim]")
+
+
 @cli.command()
 @click.option(
     "--provider",