[FEATURE][Desktop]: Show a persistent indicator when auto-accept permissions is active, and make the setting a real default for new sessions

Describe the enhancement you want to request

Problem

Since v1.4.0 (#23586), auto-accept permissions is toggled via Settings → General or the command palette (Cmd+Shift+A), but once enabled there is no persistent visual indication in the session UI that subsequent tool calls run without approval. The only feedback is a one-time toast. This leads to two issues:

1. Safety / awareness. There is no way to tell at a glance that the current session auto-approves permission requests — for example after toggling it via the keybind by accident, or when returning to a session started earlier. Other agent harnesses address this with a persistent status indicator (e.g. Claude Code shows its "bypass permissions" mode in the status line).
2. Confusing persistence. As noted in #25642, the Settings toggle looks like a global preference but effectively resets for new sessions, because toggling it inside a session is session-scoped. Users who want auto-accept as their default workflow have to re-enable it constantly.

Relation to previous requests

I'm aware of #21578, #25642 and #21423 (closed as not planned), which asked to restore the per-session toggle button in the session UI. This request is deliberately different: it does not ask to bring back per-session controls, and keeps the v1.4.0 design direction. It only asks to (a) surface the already tracked auto-accept state and (b) make the already existing setting behave predictably.

Proposal

1. Persistent indicator while auto-accept is active. A small badge in the prompt footer, next to the model/variant selector — e.g. ⚡ Auto-accept (icon + short label, distinct styling, tooltip: "Permission requests are being auto-approved"). The state is already available (permission.isAutoAccepting(sessionID, directory) / isAutoAcceptingDirectory), so this is a read-only visualization of existing state with no changes to permission logic. Optionally, clicking the badge could disable auto-accept or explain how to turn it off.
2. Make the Settings toggle an honest default for new sessions. When auto-accept is enabled globally (Settings → General, outside a session), persist it so that new sessions start with auto-accept on until it is explicitly disabled. This matches the mechanism already used for permission: "allow" in config (enableConfiguredDirectory) and resolves the confusion described in #25642 — without adding any new controls to the session UI.

The two parts complement each other: a persistent default is only good UX when its state is constantly visible — which is exactly what the indicator provides.

Benefits

• Users always know when OpenCode acts without asking — fewer "surprise" approvals. Related: #15589, where auto-accept re-enabling unexpectedly was reported as a bug; a visible indicator makes such behavior immediately explainable.
• Power users get a stable "auto-accept by default" workflow without re-toggling every session.
• No regression of the v1.4.0 simplification: zero new per-session controls, just one small read-only badge.
• Better discoverability of the feature for new users.

Environment

OpenCode Desktop 1.18.4, macOS