feat: add Agent Teams support and token usage fuel gauges

[ErickGross-19]

Backend (extension):

• src/constants.ts: add Agent/TeamCreate/TeamDelete/SendMessage tool name constants and TEAMMATE_MATCH_WINDOW_MS
• src/types.ts: make terminalRef optional for teammates; add inputTokens, outputTokens, and team fields to AgentState and PersistedAgent
• src/teamManager.ts: new module — registerPendingTeammate, tryClaimJsonlForTeammate, markAgentAsLead, getTeammatesForLead, handleSendMessage, clearExpiredPending
• src/transcriptParser.ts: detect Agent/TeamCreate/SendMessage tool events; extract token usage; expand PERMISSION_EXEMPT_TOOLS
• src/fileWatcher.ts: call tryClaimJsonlForTeammate before /clear logic
• src/agentManager.ts: persist/restore teammates; re-send token/lead on reconnect
• src/PixelAgentsViewProvider.ts: despawn all teammates on lead terminal close

Webview:

• webview-ui/src/constants.ts: team label, fuel gauge, token threshold constants
• webview-ui/src/office/types.ts: add team + token fields to Character; add 'message' bubble type
• webview-ui/src/office/engine/characters.ts: init inputTokens/outputTokens
• webview-ui/src/office/engine/officeState.ts: addAgent teamFields param; markAsLead, setAgentTokens, showSendMessageBubble; tick 'message' bubbles
• webview-ui/src/hooks/useExtensionMessages.ts: handle agentIsLead, teammateCreated, teammateRemoved, agentSendMessage, agentTokenUsage
• webview-ui/src/office/engine/renderer.ts: renderCharacterLabels — LEAD/role badge and color-coded fuel gauge per character