feat(v0.6): launch path carries ResolvedAgent (command + args + env)

LaunchOpts.Agent (string) and WorkspaceEntryOptions.Agent (string) are
replaced by *agent.Resolved, carrying Command, Args, and Env. The five
entry commands (new, resume, last, open, attach) each construct an
AgentSpec from the workspace metadata, apply --agent as a one-shot
agent.command override (Open Q 1 — keeps muscle memory for users
passing executable paths), call agent.Resolve, and pass the result
through. resolveEntryAgent centralises the resume/last/open/attach path.

shell.ExecAgent and shell.ExecTmuxAgent gain an args parameter; agent.env
is merged into the env map at the session.Run launch switch, AFTER
ctask's exported CTASK_* vars (per spec §5: agent.env wins on collision).
mergeAgentEnv is the centralised merge.

Lease, manifest, write lock, heartbeat, summary, and provisional
cleanup are unchanged. The Agent string fields on Lease, SessionSummary,
and SessionInfo continue to record the launched command for diagnostics.

cmd/entry.go

@@ -7,6 +7,7 @@ import (
 	"path/filepath"
 	"runtime"
 
+	"github.com/warrenronsiek/ctask/internal/agent"
 	"github.com/warrenronsiek/ctask/internal/config"
 	"github.com/warrenronsiek/ctask/internal/session"
 	"github.com/warrenronsiek/ctask/internal/shell"
@@ -23,14 +24,14 @@ type WorkspaceEntryOptions struct {
 	WsPath           string              // absolute workspace directory
 	WsRoot           string              // top-level root (used for CTASK_ROOT env var)
 	WsMeta           *workspace.TaskMeta // workspace metadata
-	Agent            string
-	Shell            bool   // launch interactive shell (open / new --shell)
-	Force            bool   // bypass v0.4 Layer 1/3 prompts (owner-create only)
-	Direct           bool   // user passed --direct
-	AlwaysPersistent bool   // ctask attach: ignore CTASK_SESSION_MODE
-	CommandName      string // for hint rendering: "new" | "resume" | "open" | "attach"
-	TmuxPath         string // pre-resolved tmux path; if empty in persistent mode, runWorkspaceEntry resolves
-	NewlyCreated     bool   // forwarded to LaunchOpts.NewlyCreated
+	ResolvedAgent    *agent.Resolved     // launch-ready agent (command + args + env)
+	Shell            bool                // launch interactive shell (open / new --shell)
+	Force            bool                // bypass v0.4 Layer 1/3 prompts (owner-create only)
+	Direct           bool                // user passed --direct
+	AlwaysPersistent bool                // ctask attach: ignore CTASK_SESSION_MODE
+	CommandName      string              // for hint rendering: "new" | "resume" | "open" | "attach"
+	TmuxPath         string              // pre-resolved tmux path; if empty in persistent mode, runWorkspaceEntry resolves
+	NewlyCreated     bool                // forwarded to LaunchOpts.NewlyCreated
 }
 
 // runWorkspaceEntry is the test seam for the persistent-mode dispatcher.
@@ -114,6 +115,18 @@ func defaultRunWorkspaceEntry(opts WorkspaceEntryOptions) error {
 	return fmt.Errorf("internal: unreachable persistent dispatch")
 }
 
+// resolveEntryAgent builds the launch-ready agent for an entry command
+// (resume / last / open / attach). It starts from the workspace's
+// AgentSpec, applies an optional one-shot agent.command override (the
+// --agent flag — a command override, NOT a type selector, per v0.6
+// Open Question 1), then resolves against the user-level default_agent.
+func resolveEntryAgent(spec workspace.AgentSpec, commandOverride string) (*agent.Resolved, error) {
+	if commandOverride != "" {
+		spec.Command = commandOverride
+	}
+	return agent.Resolve(spec, config.LoadResolver().DefaultAgent().Value)
+}
+
 func entryEnvVars(opts WorkspaceEntryOptions) map[string]string {
 	return config.EnvVars(
 		opts.WsMeta.Slug, opts.WsMeta.Mode,
@@ -127,7 +140,7 @@ func invokeDirectRun(opts WorkspaceEntryOptions) error {
 	return session.Run(session.LaunchOpts{
 		WsDir:           opts.WsPath,
 		EnvVars:         entryEnvVars(opts),
-		Agent:           opts.Agent,
+		ResolvedAgent:   opts.ResolvedAgent,
 		Mode:            opts.WsMeta.Mode,
 		Slug:            opts.WsMeta.Slug,
 		Shell:           opts.Shell,
@@ -175,35 +188,35 @@ func formatDirectModeTmuxHint(slug string) string {
 
 func invokePersistentRun(opts WorkspaceEntryOptions, tmuxPath, sessionName string) error {
 	return session.Run(session.LaunchOpts{
-		WsDir:        opts.WsPath,
-		EnvVars:      entryEnvVars(opts),
-		Agent:        opts.Agent,
-		Mode:         opts.WsMeta.Mode,
-		Slug:         opts.WsMeta.Slug,
-		Shell:        opts.Shell,
-		LaunchDir:    opts.WsMeta.LaunchDir,
-		Category:     opts.WsMeta.Category,
-		SessionMode:  "persistent",
-		SessionName:  sessionName,
-		TmuxPath:     tmuxPath,
-		Force:        opts.Force,
-		NewlyCreated: opts.NewlyCreated,
+		WsDir:         opts.WsPath,
+		EnvVars:       entryEnvVars(opts),
+		ResolvedAgent: opts.ResolvedAgent,
+		Mode:          opts.WsMeta.Mode,
+		Slug:          opts.WsMeta.Slug,
+		Shell:         opts.Shell,
+		LaunchDir:     opts.WsMeta.LaunchDir,
+		Category:      opts.WsMeta.Category,
+		SessionMode:   "persistent",
+		SessionName:   sessionName,
+		TmuxPath:      tmuxPath,
+		Force:         opts.Force,
+		NewlyCreated:  opts.NewlyCreated,
 	})
 }
 
 func invokePersistentAdoption(opts WorkspaceEntryOptions, tmuxPath, sessionName string) error {
 	return session.AdoptExistingPersistentSession(tmuxPath, sessionName, opts.WsPath, session.LaunchOpts{
-		WsDir:       opts.WsPath,
-		EnvVars:     entryEnvVars(opts),
-		Agent:       opts.Agent,
-		Mode:        opts.WsMeta.Mode,
-		Slug:        opts.WsMeta.Slug,
-		Shell:       opts.Shell,
-		LaunchDir:   opts.WsMeta.LaunchDir,
-		Category:    opts.WsMeta.Category,
-		SessionMode: "persistent",
-		SessionName: sessionName,
-		TmuxPath:    tmuxPath,
+		WsDir:         opts.WsPath,
+		EnvVars:       entryEnvVars(opts),
+		ResolvedAgent: opts.ResolvedAgent,
+		Mode:          opts.WsMeta.Mode,
+		Slug:          opts.WsMeta.Slug,
+		Shell:         opts.Shell,
+		LaunchDir:     opts.WsMeta.LaunchDir,
+		Category:      opts.WsMeta.Category,
+		SessionMode:   "persistent",
+		SessionName:   sessionName,
+		TmuxPath:      tmuxPath,
 	})
 }