feat: persist terminal sessions on window reload

[j4rviscmd]

Summary

Add coderm.terminal.persistSessionOnReload (default: true) to fully restore terminal sessions on window reload even when terminal.integrated.enablePersistentSessions is disabled. close/quit still discards sessions per the upstream setting.

Problem

When terminal.integrated.enablePersistentSessions: false, reload window discards all terminal state but leaves an empty pane — the terminal UI frame remains with a fresh shell inside, losing cwd, child processes, scrollback, and the pane split layout.

Solution

Wrap TerminalConfigurationService via DI override (CodermTerminalConfigurationService) to force config.enablePersistentSessions to true in reload-relevant contexts, reusing the existing VSCode persistence paths (pty host detach/reattach, layout info, editor serializer).

Behavior matrix (when the coderm setting is enabled AND the user setting is false):

• Normal operation / reload startup: force true so processes are created with shouldPersist=true (reload detach requires this at process-creation time) and reconnection is enabled
• Reload shutdown (reason === RELOAD): force true so processes detach and survive
• Non-reload shutdown (CLOSE/QUIT/LOAD): pass through false so processes are disposed and buffer revival is skipped, matching the user's enablePersistentSessions: false intent

Race-free guarantee: this service IS ITerminalConfigurationService, so DI instantiates it before any consumer (e.g. TerminalService). The onBeforeShutdown listener here registers before consumers', and Emitter.fire() dispatches synchronously, so _shutdownReason is set before any consumer reads config during shutdown.

DI override: coderm.contribution.ts is imported AFTER terminal.contribution.ts in workbench.common.main.ts, and ServiceCollection.set() is last-wins, so the coderm registerSingleton replaces the upstream descriptor.

Changes

• New src/vs/workbench/contrib/coderm/browser/terminalPersistSessionOnReload.ts: setting registration + CodermTerminalConfigurationService wrapper + registerSingleton (last-wins DI override)
• src/vs/workbench/contrib/coderm/browser/coderm.contribution.ts: side-effect import
• src/vs/workbench/contrib/terminal/browser/terminalEditorInput.ts: alignment fix — read enablePersistentSessions via ITerminalConfigurationService.config (was the only outlier using IConfigurationService.getValue directly, which bypassed the wrapper)
• README.md / README.ja.md: add the setting to the Coderm settings table

Why DI override (not editing each guard site)

enablePersistentSessions is read at 8+ sites (terminalService.ts, terminalProcessManager.ts, ...). Wrapping the single config getter localizes the Coderm diff to one file and minimizes upstream-merge conflicts — consistent with the project's "localize the diff" fork policy.

Verification

Tested locally with terminal.integrated.enablePersistentSessions: false:

• Multiple terminals (panel split panes + editor), each with cwd changes and scrollback → reload window → all fully restored (process, cwd, scrollback, pane layout)
• Close/quit → terminals discarded (reload-only persistence confirmed)
• coderm.terminal.persistSessionOnReload: false → restores upstream behavior

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