fix(core): isolate shell jobs by shell ID - #45985

Summary

Give each shell process its own job, keyed by its existing shell ID instead of the enclosing tool-call ID. Parallel shell calls inside one CodeMode execution currently share that tool-call ID, so the job service joins unrelated commands and some calls never receive their result.

• Use the returned job ID for background completion observers; keep permission attribution and plugin hook IDs unchanged.
• Match desktop/web background-task completion and TUI completion navigation by shell ID, preserving legacy tool-call-ID matching for saved messages.
• Keep one focused parallel-shell regression and update existing background-notification, restart-recovery, and TUI navigation tests.

No new metadata fields or schema changes. Background completion jobID now identifies the shell job; shellID remains the stable link to the command. Subagent jobs, the default CodeMode tool configuration, and nested output rendering are unchanged.

Validation

• Core: shell, CodeMode, job, subagent, and session execution suites — 114 passed, 36 platform/tool-dependent skips. Run with SHELL=/bin/bash on this host.
• TUI: session-row suite — 20 passed, including shell-ID and legacy-ID navigation.
• App: existing request/session model suites — 18 passed.
• Package typechecks: core, TUI, and app.
• The focused parallel-shell regression times out with the original job key and passes with the fix.

Production-build tab-switch benchmark remains inconclusive: two of three baseline samples and one of three final samples completed; the others timed out. No performance improvement or full browser-validation claim is made.

Requested by: @rekram1-node (Aiden via Slack)