candiedyaml: honour !!str tag in resolveInterface to prevent YAML 1.1 bool coercion

[ivzhelev]

Problem

resolveInterface in legacy/candiedyaml/resolver.go ignores an explicit !!str tag when dispatching scalar values. A scalar such as !!str off has event.tag = "tag:yaml.org,2002:str" and event.implicit = false, but the existing guard at line 367:

if len(event.tag) == 0 && !event.implicit {
    return "", val
}

does not fire — because len(event.tag) != 0. The function then falls through to the character-based type dispatch, where 'o' matches the bools byte set and resolve_bool("off") succeeds, returning (yaml_BOOL_TAG, false).

The result: any YAML emitter that writes !!str off (the standard way to protect a YAML 1.1 boolean-colliding value) produces data that candiedyaml decodes as bool(false) instead of string("off"). Any downstream code relying on string semantics (jq paths like .config.basic_auth_handling // "default", string comparisons) then silently fails.

Fix

Add an early-return guard for the !!str tag immediately after the existing implicit/no-tag guard:

// Honour an explicit !!str tag: the YAML spec requires that an explicit
// tag overrides implicit type resolution.
if string(event.tag) == yaml_STR_TAG {
    return yaml_STR_TAG, val
}

This is a 3-line change. All other type dispatch (int, float, bool, null, binary, timestamp) is unchanged.

The resolve() function for typed decodes is unaffected — it dispatches on the target Go reflect.Kind before calling resolveInterface, so resolve_bool still handles !!bool off and decoding !!str off into a bool field still returns the expected error.

Tests

Adds a new Ginkgo context "Explicit !!str tag preserves string (no bool coercion)" in resolver_test.go covering all 16 YAML 1.1 boolean tokens (on, ON, off, OFF, yes, YES, no, NO, true, TRUE, false, FALSE, y, Y, n, N) tagged with !!str.

Fixes #38