v2: port the Agent Manager settings tab #15797

Part of #15315. Follow-up to the Agent Manager port in #15737.

The Agent Manager settings tab is the one ported surface that is still missing. The extension contributes the kilo-code.v2.agentManager.* settings, but the settings UI has no Agent Manager section, so users can only change them through settings.json.

Current state on v2:

• packages/kilo-vscode/webview-ui/src/v2/settings-config.tsx lists agentManager.autoBranchNaming, agentManager.branchPrefix, agentManager.worktreePool and agentManager.pushFixes in a type union, with no rows.
• The Agent Manager gear opens Settings without an Agent Manager tab, and the settings navigation drops projectId, so it cannot target the project the panel belongs to.
• kilo-code.v2.showShortcutHints has no settings row and is absent from KiloSettingKey.
• The agentManager write allowlist carries showTaskTimeline, which the panel never posts, and omits settings a ported tab would need.
• The full gap list with file references is in .kilo/plans/agent-manager-v2-audit.md, section 6.

Work:

• Port the v1 Agent Manager settings tab and its rows with the v1 labels, descriptions and order (read main with git show main:<path>).
• Make the panel gear open that tab for the right project (keep projectId through SettingsNavigation).
• Add the showShortcutHints row and KiloSettingKey entry.
• Align the agentManager write allowlist with the settings the tab and panel actually post.
• Keep the intent of fix(vscode): gate settings write scope and record map gaps #15652 (gate settings write scope).

Done when the gear opens the Agent Manager tab for the panel's project, every row reads and writes its setting with the v1 defaults, and the sidebar and panel honor the same values. Prove it with a VS Code self-test screenshot of the tab beside v1.