QuiltSync error page shows raw AWS SDK error chain instead of human-readable message

[drernie]

Problem

When an S3 operation fails, QuiltSync renders the full raw AWS SDK error chain directly in the UI. This includes internal Rust types (ServiceError, HeaderValue, SdkBody, escaped JSON strings, etc.) that are meaningless to end users.

The error message can be several kilobytes of noise that buries the actual failure reason.

Affected code

• quilt-rs/src/error.rs:207 — S3(Option<Host>, S3Error) uses {0:?} debug formatting for the host, printing None or Some(Host { inner: ... }) verbatim
• quilt-rs/src/io/remote/s3.rs:59 — Error::S3Raw wraps the full DisplayErrorContext output
• quilt-sync/src/templates/pages/error.html:14 — renders {{ err | safe }} with no truncation or formatting

Cases to handle

Two known concrete cases are documented in comments on this issue.

Proposed fix

• Extract just the AWS error code and message fields and surface those
• Replace {0:?} debug formatting on Option<Host> with a human-readable equivalent (e.g. "no catalog" vs the host domain)
• For InvalidAccessKeyId with host: None (local ~/.aws creds), show a specific message: "Your AWS credentials are invalid. Please update ~/.aws/credentials."

[drernie]

Case 1: InvalidAccessKeyId — invalid local AWS credentials

User-reported log from 2026-02-26:

ERROR quilt_sync::commands: Quilt error: S3 error for None: Failed to get object stream: S3 error: service error: unhandled error (InvalidAccessKeyId): Error { code: "InvalidAccessKeyId", message: "The AWS Access Key Id you provided does not exist in our records.", s3_extended_request_id: "aCMWiGvUuJO5awuJ6Bw1rci+Yzl7bUaf07jZcWt8LmCGqb46lt1hnjrAVErA2HFNVi/FfciR4os=", aws_request_id: "NCEP2SB9F25TAC81" } ...

Root cause: The S3 URI had no &catalog= parameter, so QuiltSync used ~/.aws credentials. The IAM access key AKIAX4DFMJZGXX565NEF has been deleted or rotated. host is None in this path, so no Login button is shown — the user gets a wall of raw SDK output with no actionable guidance.

What the user should see: "AWS credentials in ~/.aws are invalid (InvalidAccessKeyId). Please update your credentials."

[drernie]

Case 2: NoSuchKey — missing S3 object

Screenshot from nightly.quilttest.com (2026-02-27):

The error page showed:

Quilt error: S3 error for Some(Host { inner: Domain("nightly.quilttest.com") }): Failed to get object stream: S3 error: service error: NoSuchKey: The specified key does not exist.: NoSuchKey: The specified key does not exist. (ServiceError(...)) (S3Raw("..."))

Root cause: A Quilt catalog-authenticated request tried to read .quilt/named_packages/horizon/2026-03-23/latest — a future-dated path that doesn't exist in S3. host is Some("nightly.quilttest.com") so a Login button is rendered, but it's not the right recovery action for a missing object.

What the user should see: "Package not found: the requested version does not exist." (The future date in the path may also indicate a separate bug where a package tag references a not-yet-published revision.)