feat: inject effort as soft default via CLI flags instead of env var (#104)

CLAUDE_CODE_EFFORT_LEVEL hard-locks effort for the whole session and makes
Claude reject in-session /effort switching (incl. ultracode). Carry effort
as a dedicated payload field instead, injected at spawn as a soft default:

- regular levels (incl. max) -> claude --effort <level>
  (the settings effortLevel key is enum([low,medium,high,xhigh]) with
  .catch(undefined), so max would be silently dropped there)
- ultracode -> claude --settings '{"ultracode":true}'
  (dedicated boolean settings key, rejected by the --effort flag)

Changes:
- add effort enum field to create/quick-start/ralph-loop schemas and thread
  it through Session -> CreateSessionOptions/RespawnPaneOptions -> spawn
- buildEffortCliArgs() in session-cli-builder, shared by tmux spawn command
  and direct-PTY fallback args
- frontend: buildEnvOverrides() no longer emits CLAUDE_CODE_EFFORT_LEVEL;
  validated effort goes into payloads via getEffortSetting()
- settings UI: add Ultracode option to the Thinking Effort dropdown
- legacy migration: Session constructor extracts CLAUDE_CODE_EFFORT_LEVEL
  from persisted envOverrides; applyEnvOverrides() unsets the stale tmux
  session var so respawned panes are no longer locked
- tests: test/effort-injection.test.ts (13 cases)

Co-authored-by: Teigen <teigenzhang@gmail.com>

src/web/public/terminal-ui.js

@@ -1244,7 +1244,9 @@ Object.assign(CodemanApp.prototype, {
       // Match by path (not basename) so linked/renamed cases still resolve correctly.
       const matchingCase = (this.cases || []).find((c) => c.path === workingDir);
       const caseName = matchingCase?.name || workingDir.split('/').pop() || '';
-      const envOverrides = this.buildEnvOverrides(this.getCaseSettings(caseName), this.loadAppSettingsFromStorage());
+      const globalSettings = this.loadAppSettingsFromStorage();
+      const envOverrides = this.buildEnvOverrides(this.getCaseSettings(caseName), globalSettings);
+      const effort = this.getEffortSetting(globalSettings);
       const createRes = await fetch('/api/sessions', {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
@@ -1253,6 +1255,7 @@ Object.assign(CodemanApp.prototype, {
           name,
           resumeSessionId: sessionId,
           ...(Object.keys(envOverrides).length > 0 ? { envOverrides } : {}),
+          ...(effort ? { effort } : {}),
         }),
       });
       const createData = await createRes.json();