[lore 1/7] repo scaffold and core types

[kunallanjewar]

Summary

Bootstraps mathomhaus/lore with the type surface every later quest in the
v0.1.1 series builds on. Library-only scope: no CLI, no MCP server, no
service.

• go.mod at module path github.com/mathomhaus/lore, Go 1.23 minimum, no
  external dependencies yet (interfaces and reference impls land in
  subsequent quests, which is when OpenTelemetry and modernc.org/sqlite
  enter the require block).
• pkg/lore/doc.go: package doc that frames the library scope and the three
  pluggable interfaces (Store, Embedder, VectorStore) that compose a
  Retriever and an optional Ingester.
• pkg/lore/kind.go: Kind typed string with the eight canonical constants
  (decision, principle, procedure, reference, explanation,
  observation, research, idea), AllKinds(), and Validate() that
  wraps ErrInvalidKind.
• pkg/lore/errors.go: sentinel errors (ErrNotFound, ErrDuplicate,
  ErrInvalidKind, ErrInvalidArgument, ErrConflict, ErrUnsupported,
  ErrClosed). Distinct so callers can errors.Is without ambiguity.
• pkg/lore/lore.go: Entry, Edge, SearchHit, ListOpts, SearchOpts.
  Each field documents nullable / slice / map semantics so Store
  implementations can persist them consistently.
• README.md: positioning paragraph, install hint, pre-v1.0 stability
  disclaimer, attribution to mathomhaus/guild, link to the spec.
• .gitignore tuned for Go.
• .github/workflows/ci.yml: matrix on Go 1.23 and 1.24 across Ubuntu and
  macOS, runs go vet, go build, and go test -race -count=1.

Acceptance criteria addressed

• go.mod at github.com/mathomhaus/lore, Go 1.23+
• LICENSE Apache 2.0 verified at root (untouched from gh repo create)
• .gitignore for Go projects
• README scaffold with positioning, install hint, pre-v1.0 disclaimer,
  attribution to mathomhaus/guild, link to spec doc
• pkg/lore/lore.go: Entry, Edge, SearchHit, common opts types
• pkg/lore/kind.go: Kind typed string + 8 canonical constants +
  Validate()
• pkg/lore/errors.go: sentinel errors using errors.New and
  fmt.Errorf wrap-friendly
• pkg/lore/doc.go: package-level godoc explaining scope and the three
  swap points
• .github/workflows/ci.yml: Go matrix 1.23+, runs vet, test, build
• All files Apache 2 compatible (no per-file headers required)
• Branch quest-1-scaffold, PR opened

Test plan

• go vet ./... clean
• go build ./... clean
• go test -race -count=1 ./... passes (16 tests, including 8
  canonical-kind subtests)
• gofmt -l . reports no diffs
• CI green on Ubuntu and macOS, Go 1.23 and 1.24

Notes

• go.mod deliberately has no require block at this point. Adding
  unused deps (OpenTelemetry, etc.) just to satisfy a future need would be
  scrubbed by go mod tidy. They land in quest 2 (sqlite) and quest 3 (BGE)
  when actually imported.
• The kind taxonomy uses 8 values immediately, not the legacy 5. The spec
  note about "5 kinds for fork-and-strip speed" is moot here since this is
  a clean rewrite, not a fork.
• errors.go is hand-written so errors.Is and fmt.Errorf("%w") work
  cleanly across all callers; tests prove distinctness and wrap behavior.