feat(observability): restore monitoring coverage, make gaps visible, stream executions

Monitoring coverage was 3 of 89 active entities. Three bugs, each hidden by
discarded errors in checkdefaults:

- writeCheck generated a fresh uuid, inserted the check entity ON CONFLICT
  (slug) DO NOTHING, then wrote a check_defs row referencing it. On any
  re-seed the slug already existed, the entity insert no-oped, and the FK
  violated — aborting the ingest transaction and surfacing as an unrelated
  failure several entities later. Re-seeding has been broken since; prod's
  coverage was frozen at its first successful seed. This is what
  TestSeedIngestIdempotentAndNoDuplicateEdges had been reporting.
- shortSlug truncated to the last 8 chars, so all 21 ingress routes collapsed
  to ".network" and overwrote each other; service:jellyfin collided with
  lxc:jellyfin.
- The ssh-script checker never read the `args` config checkdefaults wrote, so
  process_check.sh always ran without its unit name and returned "unknown".

Coverage is now 75/89. Monitoring is declared per entity type in
seeds/ontology.yaml and resolved through the is-a hierarchy, so a type can say
it warrants nothing (site, lan, mesh, cluster) and never be reported as a gap.
coverageSweep raises an `unmonitored` signal only where a type declares
monitoring it lacks — 8 real gaps, no false positives.

Also:
- entity_types.attribute_schema was never ingested: the seed loader read
  "attribute_schema" but the YAML says "attributes", so all 60 types stored
  JSON null.
- ListExecutions ignored its declared target/action/correlation_id filters and
  paginated on a non-unique target slug, dropping and repeating rows.
- started_at was captured but only written at terminal state, so a running
  execution reported NULL for its whole life. The three MCP auto-run copies
  wrote no timing at all; they are now one autoRun helper.
- SSH output was buffered to completion and discarded entirely on timeout.
  Both sshExec copies now stream through a shared execlog sink into
  execution_logs, and keep partial output when a command is cancelled.
- executions.correlation_id was a random per-execution uuid that correlated
  nothing; it is now the chat session id, which is what lets the chat tail
  live output.
- reversible_low had no auto-run branch despite policy declaring it
  unattended. Since computeCommandRisk never returns it, the class only arises
  when an agent declares it over a read_only command — so gating it penalised
  candor without adding safety.
- backup-target gains a backup-freshness checker (portable find -mmin, since
  the first target is on macOS), resolving its host by walking backs-up-to
  backwards. The pre-deploy pg_dump is now a tracked backup target.

UI: an Executions section on entity detail with live output tailing, and
streamed output under a running `run` call in the chat timeline.

Migrations 022-024. Ops.svelte and context.ts exclude execution.output from
their refetch triggers, which would otherwise fire once a second per command.

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

internal/execlog/execlog.go

@@ -0,0 +1,135 @@
+// Package execlog persists incremental command output for an execution and
+// announces it on the event stream.
+//
+// It exists as its own package because both SSH execution paths need it —
+// internal/mcp (the agent's auto-run windows) and internal/httpapi (the
+// post-approval actuator). Those two already carry near-identical copies of
+// sshExec, and every bug found in this area so far has been a case of the two
+// copies drifting apart; one shared sink is the cheap way not to repeat that.
+package execlog
+
+import (
+	"context"
+	"log/slog"
+	"sync"
+	"time"
+
+	"github.com/dtoro/oikos/internal/db"
+	"github.com/dtoro/oikos/internal/db/sqlcgen"
+	"github.com/dtoro/oikos/internal/observability"
+	"github.com/google/uuid"
+)
+
+// eventInterval throttles execution.output events. Chunks are persisted as
+// they arrive, but a chatty command (apt, a long build) can produce hundreds
+// per second and the SSE broker drops events for slow subscribers — flooding
+// it would push out the signal.* and approval.* events that actually need to
+// arrive. The event is only a "there is more output" ping; subscribers re-read
+// the rows.
+const eventInterval = time.Second
+
+// Sink receives output chunks as they arrive from a remote command.
+type Sink func(stream string, chunk []byte)
+
+// New returns a Sink that writes chunks to execution_logs and emits a
+// throttled execution.output event, plus a Flush to call when the command
+// finishes.
+//
+// The returned Sink is safe for concurrent use: stdout and stderr are written
+// from separate goroutines.
+func New(ctx context.Context, pool *db.Pool, execID uuid.UUID, correlationID string) (Sink, func()) {
+	var (
+		mu        sync.Mutex
+		seq       int
+		lastEvent time.Time
+		pending   bool
+	)
+
+	emit := func() {
+		if err := observability.Event(ctx, sqlcgen.New(pool), "execution.output", &execID,
+			"info", "actuator", correlationID, map[string]any{"execution_id": execID.String()}); err != nil {
+			slog.Debug("execlog: emit output event", "error", err, "execution_id", execID)
+		}
+	}
+
+	sink := func(stream string, chunk []byte) {
+		if len(chunk) == 0 {
+			return
+		}
+		mu.Lock()
+		seq++
+		n := seq
+		mu.Unlock()
+
+		// A failed log write must never fail the command: this is observability,
+		// and the authoritative output still lands in executions.result at the
+		// end. Log and carry on.
+		if _, err := pool.Exec(ctx,
+			`INSERT INTO execution_logs (execution_id, seq, stream, chunk)
+			 VALUES ($1, $2, $3, $4)`,
+			execID, n, stream, string(chunk)); err != nil {
+			slog.Debug("execlog: persist chunk", "error", err, "execution_id", execID)
+			return
+		}
+
+		mu.Lock()
+		due := time.Since(lastEvent) >= eventInterval
+		if due {
+			lastEvent = time.Now()
+			pending = false
+		} else {
+			pending = true
+		}
+		mu.Unlock()
+
+		if due {
+			emit()
+		}
+	}
+
+	// Flush emits a final event when output arrived inside the throttle window,
+	// so the last few lines of a short command are not left unannounced.
+	flush := func() {
+		mu.Lock()
+		due := pending
+		pending = false
+		mu.Unlock()
+		if due {
+			emit()
+		}
+	}
+
+	return sink, flush
+}
+
+// Read returns an execution's persisted output in order.
+func Read(ctx context.Context, pool *db.Pool, execID uuid.UUID, limit int) ([]Chunk, error) {
+	if limit <= 0 {
+		limit = 1000
+	}
+	rows, err := pool.Query(ctx,
+		`SELECT seq, stream, chunk, ts FROM execution_logs
+		 WHERE execution_id = $1 ORDER BY seq LIMIT $2`, execID, limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var out []Chunk
+	for rows.Next() {
+		var c Chunk
+		if err := rows.Scan(&c.Seq, &c.Stream, &c.Chunk, &c.TS); err != nil {
+			return nil, err
+		}
+		out = append(out, c)
+	}
+	return out, rows.Err()
+}
+
+// Chunk is one persisted slice of command output.
+type Chunk struct {
+	Seq    int       `json:"seq"`
+	Stream string    `json:"stream"`
+	Chunk  string    `json:"chunk"`
+	TS     time.Time `json:"ts"`
+}