feat(desktop): true single-process mode (option c)

[rickylabs]

Part of #327

Handle: #E4 · Milestone: 0.0.1-beta.8 · Depends on: #E1, #E3 (and #E2 for the shell). Blocks: #E5, #E7, #E6.

Scope — true single-process mode (option c)

Wire the packaged desktop dashboard's service clients through transport:{mode:'in-process'} so the backend runs in-process; a single generated flag flips web↔desktop. Config-driven link-mode default (NETSCRIPT_LINK_MODE / generated config).

Acceptance

1. Packaged binary serves the dashboard with zero external service process and zero loopback RPC for in-process-mounted services; verified by asserting no listener is opened for them.
2. Generated dashboard client code is identical web vs desktop except the link-mode flag.
3. End-to-end: launch packaged binary → dashboard renders → a data-plane operation round-trips through the in-process link to the single-writer db and back.

Design source: design/E-desktop/epic-and-issues.md (#E4).

[rickylabs]

Dependency edge (DAG second pass): Depends on #451 (E1), #453 (E3), and #452 (E2) for the shell.