fix: retain undelivered marker on new messages

[Pleasurecruise]

Related issue

Fix #47

Problem / pressure

PR #74 made lastMissingHistoryUserMsgId a permanent negative acknowledgement for an undelivered turn, but missed the ordinary new-message path:

1. Message A times out waiting for history and is blocked by the marker.
2. A's history entry later reaches the CLI with status: pending.
3. The user sends a different message B instead of resending A.
4. The renderer points latestUserMsgId at B but also clears A's marker.
5. The dispatcher scans pending history from oldest to newest and selects A before B.

This can execute a message the UI already presented as not delivered.

Summary

• Preserve the existing missing-history marker when the renderer publishes a different new turn.
• Keep the marker-specific resend flow responsible for terminalizing the abandoned entry.
• Tighten the renderer metadata-write test so clearing the marker fails the assertion.
• Correct the nearby comments and contributor invariants that described the old behavior.
• Rebase the change onto the latest main and resolve the contributor-invariant conflict.

Before / after

Before	After
Sending B cleared A's marker, making late pending A dispatchable again.	Sending B changes only latestUserMsgId; A remains excluded and B dispatches normally.

Test plan

• packages/components/node_modules/.bin/vitest run tests/use-session-actions.test.ts tests/resend-undelivered-dialog.test.tsx tests/undelivered-user-turn.test.ts — 34 tests passed after rebasing.
• apps/cli/node_modules/.bin/vitest run src/session/session-dispatch-logic.test.ts tests/session-dispatch-watcher.test.ts — 50 tests passed after rebasing.
• CLI and Components tsgo --noEmit passed before the rebase.
• Type-aware lint completed with 0 errors on the changed TypeScript files before the rebase.
• Prettier check passed before the rebase; git diff --check passed after conflict resolution.

Context handoff

Instructions for reviewing agents

• Review focus: Verify the metadata patch in use-session-actions.ts preserves an existing marker while moving latestUserMsgId to B.
• Decisions to challenge: Confirm retaining A's exact-ID tombstone is preferable to implicitly canceling A when the user sends unrelated B.
• Plausible failures / evidence gaps: The fix is intentionally scoped to renderer sends; CLI commands and internal dispatch producers were not changed.

Authoring context

• User goal / directives: Fix the PR fix: surface missing-history-acked messages as Not delivered with explicit resend #74 gap where sending B can revive an older not-delivered A, keep the change minimal, and explain the reproduction chain in the PR.
• Constraints / non-goals: Do not redesign dispatch state, broaden unrelated producer behavior, include dependency-store artifacts, or expose conversation transcripts.
• Risk-bearing decisions: Retain the exact-ID marker across unrelated renderer sends so A remains excluded while B still activates dispatch.
• Destructive or irreversible behavior: The product change does not migrate or delete persisted data; the PR branch was rebased onto current main to resolve conflicts.
• Deliberately not done or tested: Full repository CI was not rerun locally after the rebase; the affected Components and CLI suites were rerun instead.
• Unknowns / confidence: Confidence is high for the reported renderer path; equivalent behavior in non-renderer producers remains outside this PR's scope.