refactor(session): nuke dead sessionParams / sessionDisplayId pipeline (v43)

These columns and the messages that plumbed them existed for the CLI-
adapter era — Gemini's resume id and provider-specific session params
rode the run-finished envelope back onto the session row so the next
turn could resume. Pi Mono dispatches every provider through pi-ai and
emits neither value. The worker has been posting literal null on every
finish, finalizeRun has been writing null into task_sessions, and
rotateSession has been carrying null forward.

Remove the wire, the writer, the carry-forward, and the columns:

  - v43 migration rebuilds task_sessions without session_params_json /
    session_display_id, and runs without session_display_id. Follows
    the idempotent "create new, copy, swap, reindex" pattern used by
    v41. context_snapshot_json is preserved (also unreferenced today
    but outside this cleanup's scope).
  - RunJob / EnqueueRunPayload / ChildMessage / worker-types zod
    schema no longer carry the fields. finishRun() / createNewSession()
    signatures tighten in lockstep.
  - rotateSession starts the new session with fresh counters and no
    carry-forward.
  - turn-context resolveSession returns just the session id.
  - TaskSessionRecord / RunRecord lose the dead fields.

498/498 unit tests pass. typecheck + build clean.

src/main/database-base.ts

@@ -339,11 +339,10 @@ export class AppDatabaseBase {
   saveTask(input: { id?: string | null; companyId: string; projectId?: string | null; goalId?: string | null; parentId?: string | null; title: string; description: string; assigneeAgentId?: string | null; workspaceId?: string | null; priority: string; status: string }) { return this.tasks.saveTask(input); }
   getTask(id: string) { return this.entityCrud.getTask(id); }
   deleteTask(id: string, companyId: string) { return this.tasks.deleteTask(id, companyId); }
-  updateSessionParams(sessionId: string, sessionParams: Record<string, unknown> | null, sessionDisplayId: string | null) { return this.tasks.updateSessionParams(sessionId, sessionParams, sessionDisplayId); }
   getSessionById(sessionId: string) { return this.tasks.getSessionById(sessionId); }
   incrementSessionUsage(sessionId: string, inputTokens: number, outputTokens: number, runId: string) { return this.tasks.incrementSessionUsage(sessionId, inputTokens, outputTokens, runId); }
   archiveSession(sessionId: string, reason: string, handoffMarkdown: string) { return this.tasks.archiveSession(sessionId, reason, handoffMarkdown); }
-  createNewSession(input: { companyId: string; agentId: string; adapterType: string; sessionParamsJson: string | null; sessionDisplayId: string | null }) { return this.tasks.createNewSession(input); }
+  createNewSession(input: { companyId: string; agentId: string; adapterType: string }) { return this.tasks.createNewSession(input); }
   ensureAgentSession(input: { agentId: string; companyId: string; adapterType: string }) { return this.tasks.ensureAgentSession(input); }
   setAgentSessionId(agentId: string, sessionId: string) { return this.tasks.setAgentSessionId(agentId, sessionId); }
   getRecentRunsForTask(taskId: string, limit: number) { return this.tasks.getRecentRunsForTask(taskId, limit); }
@@ -385,7 +384,7 @@ export class AppDatabaseBase {
   readRunLog(runId: string) { return this.runs.readRunLog(runId); }
   readRunLogChunk(runId: string, offset = 0, limit = 65_536) { return this.runs.readRunLogChunk(runId, offset, limit); }
   markRunStatus(runId: string, status: RunStatus, message: string) { return this.runs.markRunStatus(runId, status, message); }
-  finishRun(input: { runId: string; status: RunStatus; summary: string | null; errorMessage: string | null; exitCode: number | null; signal: string | null; model: string | null; sessionDisplayId: string | null; unattributedCost: boolean }) { return this.runs.finishRun(input); }
+  finishRun(input: { runId: string; status: RunStatus; summary: string | null; errorMessage: string | null; exitCode: number | null; signal: string | null; model: string | null; unattributedCost: boolean }) { return this.runs.finishRun(input); }
   recordCostEntry(input: { runId: string; companyId: string; agentId: string; taskId: string | null; connectorId: string; amountUsd: number | null; unattributed: boolean }) { return this.runs.recordCostEntry(input); }
   hasActiveRun(filter: { companyId: string; taskId?: string; agentId?: string }) { return this.runs.hasActiveRun(filter); }
   listQueuedRuns() { return this.runs.listQueuedRuns(); }