fix: re-enable PNG codec for goose-mcp image handling

load_image_as_png uses ImageFormat::Png to encode non-PNG inputs
into PNG for DOCX insertion. The jpeg-only feature set broke this
at runtime for JPEG and other image formats.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jh-block

crates/goose-mcp/Cargo.toml

@@ -46,7 +46,7 @@ once_cell = { workspace = true }
 ignore = { workspace = true }
 lopdf = "0.36.0"
 docx-rs = "0.4.7"
-image = { version = "0.25", default-features = false, features = ["jpeg"] }
+image = { version = "0.25", default-features = false, features = ["jpeg", "png"] }
 umya-spreadsheet = "2.2.3"
 which = {workspace = true}
 lru = { workspace = true }