This PR expands the uri format test suite across all drafts. The expansion provides complete coverage of RFC 3986 ABNF and prose constraints. Every test was traced directly against RFC 3986 , not derived from implementation output.

Technical Coverage Details

The new cases cover every structural dimension of the grammar:

• Scheme: Valid charset, first-character rule, upper and mixed case valid (ALPHA covers %x41-5A / %x61-7A), rejection of invalid characters (~, =, /, space), %-encoding forbidden in scheme, empty-before-colon, and missing colon.
• Percent-encoding: Valid uppercase/lowercase/mixed HEXDIG triplets, double-encoding, coverage in all six URI components, rejection of non-HEXDIG, lone %, incomplete triplets, and %-encoding forbidden in port.
• Userinfo: Sub-delimiters and unreserved characters, colon-delimited forms, empty userinfo, strict first-@ split (guards against last-@ scanning bugs), slash and ? boundary tests.
• Host: reg-name fallback for malformed IPv4 per §3.2.2; all five dec-octet alternative floor/ceiling values (0–9, 10–99, 100–199, 200–249, 250–255); full/compressed/loopback/embedded-IPv4 IPv6 forms; trailing :: form; IPvFuture with uppercase V; rejection of two ::, >4 hex digits in h16, wrong group counts, misformed IPvFuture, and non-ASCII in host.
• Port: *DIGIT - empty port, leading zeros, no upper bound, rejection of +, -, space, ., alpha characters, pct-encoded digits, and Unicode decimal digits.
• Path: All five path forms; full pchar charset; rejection of gen-delims and forbidden characters ({, }, ^, `, |, \, ", <, >), control characters, and non-ASCII; dot and double-dot segments.
• Query / Fragment: pchar + / + ?; at-sign valid in both; rejection of [, ], {, ^, space, and second # in fragment; pct-encoding valid/invalid; empty and absent forms.
• URI vs URI-reference: Protocol-relative (//) and path-only relative-refs correctly rejected , format: "uri" requires an absolute URI with scheme.
• Whitespace / composites: Empty string, single space/tab/newline, leading/trailing whitespace, embedded control characters, trailing garbage, and a 2084-character URI (RFC 3986 has no length limit).

Standards & Traceability

Following the style of ipv4.json, non-obvious tests carry a comment field mentioning the relevant RFC 3986 section and ABNF production.

Triangulation note: Spot-checked against ajv-formats and python-jsonschema-format. All mismatches reflect implementation gaps against strict RFC 3986 ABNF, not errors in the test vectors.

Feedback appreciated @jviotti @jdesrosiers @karenetheridge