feat: add 'attests' edge type for skill attestations

Add new DependencyType 'attests' for skill attestations. Enables:
Entity X attests that Entity Y has skill Z at level N.

- Add DepAttests constant to dependency types
- Add AttestsMeta struct for skill, level, date, evidence, notes
- Update IsWellKnown() to include attests
- Add test cases for the new edge type

Foundation for HOP skill portability.

Closes: bd-2papc

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Executed-By: beads/crew/dave
Rig: beads
Role: crew

internal/types/types.go

@@ -649,6 +649,7 @@ const (
 	DepAuthoredBy DependencyType = "authored-by" // Creator relationship
 	DepAssignedTo DependencyType = "assigned-to" // Assignment relationship
 	DepApprovedBy DependencyType = "approved-by" // Approval relationship
+	DepAttests    DependencyType = "attests"     // Skill attestation: X attests Y has skill Z
 
 	// Convoy tracking (non-blocking cross-project references)
 	DepTracks DependencyType = "tracks" // Convoy → issue tracking (non-blocking)
@@ -672,7 +673,7 @@ func (d DependencyType) IsWellKnown() bool {
 	switch d {
 	case DepBlocks, DepParentChild, DepConditionalBlocks, DepWaitsFor, DepRelated, DepDiscoveredFrom,
 		DepRepliesTo, DepRelatesTo, DepDuplicates, DepSupersedes,
-		DepAuthoredBy, DepAssignedTo, DepApprovedBy, DepTracks,
+		DepAuthoredBy, DepAssignedTo, DepApprovedBy, DepAttests, DepTracks,
 		DepUntil, DepCausedBy, DepValidates:
 		return true
 	}
@@ -701,6 +702,22 @@ const (
 	WaitsForAnyChildren = "any-children" // Proceed when first child completes (future)
 )
 
+// AttestsMeta holds metadata for attests dependencies (skill attestations).
+// Stored as JSON in the Dependency.Metadata field.
+// Enables: Entity X attests that Entity Y has skill Z at level N.
+type AttestsMeta struct {
+	// Skill is the identifier of the skill being attested (e.g., "go", "rust", "code-review")
+	Skill string `json:"skill"`
+	// Level is the proficiency level (e.g., "beginner", "intermediate", "expert", or numeric 1-5)
+	Level string `json:"level"`
+	// Date is when the attestation was made (RFC3339 format)
+	Date string `json:"date"`
+	// Evidence is optional reference to supporting evidence (e.g., issue ID, commit, PR)
+	Evidence string `json:"evidence,omitempty"`
+	// Notes is optional free-form notes about the attestation
+	Notes string `json:"notes,omitempty"`
+}
+
 // FailureCloseKeywords are keywords that indicate an issue was closed due to failure.
 // Used by conditional-blocks dependencies to determine if the condition is met.
 var FailureCloseKeywords = []string{

internal/types/types_test.go

@@ -749,6 +749,7 @@ func TestDependencyTypeIsWellKnown(t *testing.T) {
 		{DepAuthoredBy, true},
 		{DepAssignedTo, true},
 		{DepApprovedBy, true},
+		{DepAttests, true},
 		{DepTracks, true},
 		{DepUntil, true},
 		{DepCausedBy, true},
@@ -784,6 +785,7 @@ func TestDependencyTypeAffectsReadyWork(t *testing.T) {
 		{DepAuthoredBy, false},
 		{DepAssignedTo, false},
 		{DepApprovedBy, false},
+		{DepAttests, false},
 		{DepTracks, false},
 		{DepUntil, false},
 		{DepCausedBy, false},