Add entity action and PDF download to invoices/quotes/credits/purchase-orders

These four resources are the only ones with the SDK's
entity_action_methods! route. Adds:

- `action <id> <action>` - mark_sent, mark_paid, archive, restore,
  clone_to_invoice, clone_to_quote, auto_bill, delete (routed), returning
  the updated record.
- `download <id>...` - the rendered PDF, to stdout or `--out <path>`;
  more than one id streams a single merged PDF (Invoice Ninja's bulk
  download action).

New EntityResourceArgs/EntityAction in cli.rs rather than extending the
existing ResourceArgs/Action: Rust enums don't compose, and every
resource's `run` match on Action needs to stay exhaustive without a
catch-all arm for variants it doesn't support.

Found and fixed along the way: the Download variant's --output <path>
field collided by name with the global --output table|json flag,
causing clap to panic at runtime trying to downcast the wrong type.
Renamed to --out.

Extended tests/nixos-test.nix to exercise action/download for real
against the VM. That caught a test-ordering bug of its own - asserting
mark_sent on an invoice *after* paying it off, which correctly doesn't
revert status_id from paid back to sent - fixed by reordering the
subtests. nix flake check passes clean.

Also backfills two CHANGELOG.md gaps from earlier sessions: the VM test
and CI additions had never actually been logged there.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/commands/credits.rs

@@ -3,24 +3,29 @@
 //! (Invoice Ninja stores credits in the same table/schema, distinguished by
 //! an `entity_type`), same as `quotes.rs`.
 
+use std::io::Write;
+use std::path::PathBuf;
+
 use invoiceninja_sdk::models::{Credit, ListParams};
 use invoiceninja_sdk::InvoiceNinjaClient;
 
 use crate::body;
-use crate::cli::{Action, BodyArgs, ListArgs, OutputFormat, ResourceArgs};
+use crate::cli::{BodyArgs, EntityAction, EntityResourceArgs, ListArgs, OutputFormat};
 use crate::output;
 
 pub async fn run(
     client: &InvoiceNinjaClient,
-    args: ResourceArgs,
+    args: EntityResourceArgs,
     format: OutputFormat,
 ) -> Result<(), Box<dyn std::error::Error>> {
     match args.action {
-        Action::List(list_args) => list(client, list_args, format).await,
-        Action::Get { id } => get(client, &id, format).await,
-        Action::Create(body_args) => create(client, body_args, format).await,
-        Action::Update { id, body } => update(client, &id, body, format).await,
-        Action::Delete { id } => delete(client, &id).await,
+        EntityAction::List(list_args) => list(client, list_args, format).await,
+        EntityAction::Get { id } => get(client, &id, format).await,
+        EntityAction::Create(body_args) => create(client, body_args, format).await,
+        EntityAction::Update { id, body } => update(client, &id, body, format).await,
+        EntityAction::Delete { id } => delete(client, &id).await,
+        EntityAction::Action { id, action } => do_action(client, &id, &action, format).await,
+        EntityAction::Download { ids, out } => download(client, &ids, out).await,
     }
 }
 
@@ -101,6 +106,33 @@ async fn delete(client: &InvoiceNinjaClient, id: &str) -> Result<(), Box<dyn std
     Ok(())
 }
 
+async fn do_action(
+    client: &InvoiceNinjaClient,
+    id: &str,
+    action: &str,
+    format: OutputFormat,
+) -> Result<(), Box<dyn std::error::Error>> {
+    let updated = client.credit_action(id, action).await?;
+    render(std::slice::from_ref(&updated), format)
+}
+
+async fn download(
+    client: &InvoiceNinjaClient,
+    ids: &[String],
+    out: Option<PathBuf>,
+) -> Result<(), Box<dyn std::error::Error>> {
+    let bytes = if ids.len() == 1 {
+        client.download_credit(&ids[0]).await?
+    } else {
+        client.download_credits(ids).await?
+    };
+    match out {
+        Some(path) => std::fs::write(path, bytes)?,
+        None => std::io::stdout().write_all(&bytes)?,
+    }
+    Ok(())
+}
+
 fn render(credits: &[Credit], format: OutputFormat) -> Result<(), Box<dyn std::error::Error>> {
     match format {
         OutputFormat::Json => output::print_json(credits)?,