[BUG] Add durable per-view state base for parallel tabs

[easonLiangWorldedtech]

Problem

Parallel mode in Roo Code lacks a durable per-view state foundation. When multiple webview instances run simultaneously (parallel tabs), there is no mechanism to:

1. Assign stable identities to each view instance
2. Persist non-secret selection state (mode, currentApiConfigName) across reloads
3. Merge global and per-view state in the getState() layer
4. Maintain a stable webview state ID for persistence lookups

This is the root mechanism that old Issue #908 identified, and was partially addressed by PR #909 but lacked proper per-view isolation.

Solution

Introduce a registered global setting key viewStates in globalSettingsSchema that stores only non-secret selection state:

• mode: current parallel mode
• currentApiConfigName: selected API configuration name (not full secrets)
• updatedAt: timestamp for bounded cleanup (keep most recent 50 entries)

This fixes the limitation from Issue #967 where persistence relied on scattered dynamic __view_state_* keys. Now all per-view state is properly registered in GLOBAL_STATE_KEYS, loaded via ContextProxy.initialize(), and hydrated through loadViewState() which resolves profile settings via ProviderSettingsManager.getProfile().

Scope

• Per-view identity with stable webview state ID plumbing
• viewLocalState buffer for transient per-view data
• getState() merge layer combining global + view-local state
• Durable viewStates persistence in registered global settings
• No-op compatibility: existing single-tab behavior unchanged

Tests

Targeted tests passed. Full core run: 129 files passed / 2184 passed / 9 skipped.

Notes

• No full apiConfiguration or API keys are stored in viewStates — only non-secret selections
• This is the root PR; subsequent PRs depend on this per-view state base
• Old Issue [BUG] Multi-tab mode/model settings get overwritten by latest task #908 and old PR fix(webview): isolate parallel provider view state #909 provide historical context