fix(run): address gadfly review of the phases PR

Real findings from the consensus review (37 raw; many devstral dups/noise):

- Optional/budget-salvage branches no longer swallow a context
  cancellation / deadline / critic-kill: such errors return immediately so
  the run is classified cancelled/timeout/killed, not "ok" with a fallback.
  (the most serious finding — an Optional final phase could mask a killed run)
- IsRunFunc bare phase now feeds the SHARED step observer (not just the
  audit recorder), so the critic's activity clock + Result.Steps see it —
  a long synthesize phase no longer looks idle to the critic.
- phaseModel returns the resolver's enriched (usage-attribution) context and
  the phase's calls use it, mirroring the single-loop path (non-base-tier
  phases were mis-attributed).
- salvagePhaseTranscript trims the tail on a rune boundary (was a raw byte
  slice that could split a UTF-8 rune); maxSalvage is now a named const with
  rationale.
- expandPhaseTemplate logs a WARN on parse/execute failure instead of
  silently returning the unexpanded template; documented the phase-name
  identifier requirement + the "Query" shadow.
- removed the dead phaseDeps.baseTier field.
- extracted multimodalUserMessage, shared by runAgent + the phase runner
  (was duplicated image-folding).
- aggregated phase usage is stamped onto the result even on a hard-error
  return; TrimSpace computed once; filterToolbox returns the base toolbox
  as-is for the empty-names (full-palette) case instead of copying;
  phaseModel WARN no longer prints error=<nil>.

New test: Optional phase does not swallow a cancellation. Full ./... green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

run/executor.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"strings"
 	"time"
 
 	"gitea.stevedudenhoeffer.com/steve/majordomo/agent"
@@ -344,13 +343,13 @@ func (e *Executor) Run(ctx context.Context, ra RunnableAgent, inv tool.Invocatio
 		// (Per-phase step caps are fixed — the critic's dynamic ceiling is not
 		// propagated to phases — but its steer + hard deadline still apply.)
 		runRes, runErr = e.runPhases(runCtx, ra, phaseDeps{
-			baseModel:   model,
-			baseTier:    tier,
-			baseToolbox: toolbox,
-			baseMaxIter: maxIter,
-			sharedOpts:  sharedOpts,
-			steer:       steer,
-			rec:         rec,
+			baseModel:    model,
+			baseToolbox:  toolbox,
+			baseMaxIter:  maxIter,
+			sharedOpts:   sharedOpts,
+			stepObserver: stepObserver,
+			steer:        steer,
+			rec:          rec,
 		}, input, inv.Images)
 	}
 
@@ -492,15 +491,9 @@ func runAgent(ctx context.Context, ag *agent.Agent, input string, images []llm.I
 	if len(images) == 0 {
 		return ag.Run(ctx, input, opts...)
 	}
-	parts := make([]llm.Part, 0, len(images)+1)
-	if strings.TrimSpace(input) != "" {
-		parts = append(parts, llm.Text(input))
-	}
-	for _, img := range images {
-		parts = append(parts, img)
-	}
 	// Copy opts before appending so a caller-supplied backing array is never
-	// mutated/aliased (the variadic slice can have spare capacity).
-	opts = append(opts[:len(opts):len(opts)], agent.WithHistory([]llm.Message{llm.UserParts(parts...)}))
+	// mutated/aliased (the variadic slice can have spare capacity). The multimodal
+	// opening turn (text + image parts) is built by the shared helper.
+	opts = append(opts[:len(opts):len(opts)], agent.WithHistory([]llm.Message{multimodalUserMessage(input, images)}))
 	return ag.Run(ctx, "", opts...)
 }