Add Last-Modified, pairs, and S3 headers to chunk manifest responses

Go sets Last-Modified, needle pairs, and S3 pass-through headers on
the response writer BEFORE calling tryHandleChunkedFile. Since the
Rust chunk manifest handler created fresh response headers and
returned early, these headers were missing from chunk manifest
responses. Now passes last_modified_str into the chunk manifest
handler and applies pairs and S3 pass-through query params
(response-cache-control, response-content-encoding, etc.) to the
chunk manifest response headers.

seaweed-volume/src/server/handlers.rs

@@ -1037,7 +1037,7 @@ async fn get_or_head_handler_inner(
     // Pass ETag so chunk manifest responses include it (matches Go: ETag is set on the
     // response writer before tryHandleChunkedFile runs).
     if n.is_chunk_manifest() && !bypass_cm {
-        if let Some(resp) = try_expand_chunk_manifest(&state, &n, &headers, &method, &path, &query, &etag) {
+        if let Some(resp) = try_expand_chunk_manifest(&state, &n, &headers, &method, &path, &query, &etag, &last_modified_str) {
             return resp;
         }
         // If manifest expansion fails (invalid JSON etc.), fall through to raw data
@@ -2936,6 +2936,7 @@ fn try_expand_chunk_manifest(
     path: &str,
     query: &ReadQueryParams,
     etag: &str,
+    last_modified_str: &Option<String>,
 ) -> Option<Response> {
     let data = if n.is_compressed() {
         use flate2::read::GzDecoder;
@@ -3055,6 +3056,56 @@ fn try_expand_chunk_manifest(
     response_headers.insert("X-File-Store", "chunked".parse().unwrap());
     response_headers.insert(header::ACCEPT_RANGES, "bytes".parse().unwrap());
 
+    // Last-Modified — Go sets this on the response writer before tryHandleChunkedFile
+    if let Some(ref lm) = last_modified_str {
+        if let Ok(hval) = lm.parse() {
+            response_headers.insert(header::LAST_MODIFIED, hval);
+        }
+    }
+
+    // Pairs — Go sets needle pairs on the response writer before tryHandleChunkedFile
+    if n.has_pairs() && !n.pairs.is_empty() {
+        if let Ok(pair_map) =
+            serde_json::from_slice::<std::collections::HashMap<String, String>>(&n.pairs)
+        {
+            for (k, v) in &pair_map {
+                if let (Ok(hname), Ok(hval)) = (
+                    axum::http::HeaderName::from_bytes(k.as_bytes()),
+                    axum::http::HeaderValue::from_str(v),
+                ) {
+                    response_headers.insert(hname, hval);
+                }
+            }
+        }
+    }
+
+    // S3 response passthrough headers — Go sets these via AdjustPassthroughHeaders
+    if let Some(ref cc) = query.response_cache_control {
+        if let Ok(hval) = cc.parse() {
+            response_headers.insert(header::CACHE_CONTROL, hval);
+        }
+    }
+    if let Some(ref ce) = query.response_content_encoding {
+        if let Ok(hval) = ce.parse() {
+            response_headers.insert(header::CONTENT_ENCODING, hval);
+        }
+    }
+    if let Some(ref exp) = query.response_expires {
+        if let Ok(hval) = exp.parse() {
+            response_headers.insert(header::EXPIRES, hval);
+        }
+    }
+    if let Some(ref cl) = query.response_content_language {
+        if let Ok(hval) = cl.parse() {
+            response_headers.insert("Content-Language", hval);
+        }
+    }
+    if let Some(ref cd) = query.response_content_disposition {
+        if let Ok(hval) = cd.parse() {
+            response_headers.insert(header::CONTENT_DISPOSITION, hval);
+        }
+    }
+
     // Content-Disposition
     if !filename.is_empty() {
         let disposition_type = if let Some(ref dl_val) = query.dl {