* fix: J card decodes value, stores name verbatim (#90)

The J-card parser had the escape direction inverted: it decoded the field name and exposed the value with its escape sequences intact. Both the spec (4.7.8) and canonical fossil (manifest.c) do the opposite -- defossilize only the value, compare the raw name.

Swap both the parse and marshal directions so the value round-trips decoded and the name stays verbatim.

* fix: T card escape-encodes the tag name on marshal (#91)

A tag/branch name containing a space was written verbatim, so 'my branch' produced 'T *sym-my branch *' -- a structurally valid but silently wrong card that re-parses as two tokens.

Align with canonical fossil: escape-encode the name on marshal and escape-decode it on parse, leaving the target token verbatim in both directions (4.7.16). TagCard.Name now holds the decoded form, so tagOrderKey reattaches the sign without re-decoding.

* fix: enforce two skipped T-card §4.7.16 checks on parse (#93)

parseTCard validated the sign and ordering key but accepted two malformed shapes from untrusted peers:

- a name that after the sign is entirely hex digits, indistinguishable from a hash target; - a target that is neither a valid artifact hash nor the literal '*'.

Reject both with errors (never a panic). hash.IsValidHash reuses the same target check the primary uuid path uses; the '*' and non-empty guards run first since it panics on an empty string.

* fix: T card decodes and encodes the tag value (#91), guard hex names on marshal (#93)

§4.7.16 applies the same escape rule to all three T-card tokens: the name and value are escape-decoded on parse and escape-encoded on marshal, while the target is stored verbatim. Only the name was handled; the value was passed through raw in both directions.

The read side was the real damage. `fossil branch new 'my branch'` writes

T *branch * my\sbranch T *sym-my\sbranch *

so importing an ordinary fossil repo with a spaced branch name produced a branch literally named "my\sbranch" through crosslink. Verified against the fossil binary: the artifact for that command now parses to value "my branch" and re-marshals byte-for-byte identical.

Marshal also gains the mirror of the hex-only tag name check parse already enforces. Without it a caller could build and store an artifact this repository could never read back; canonical fossil never emits one either, since it prefixes branch and user tags with "sym-". check-in: 0e579e24a4 user: [email protected] tags: trunk