refactor!: rebrand CCAM to AgentHub

Clean break, no compatibility alias. Renames the product name, the CLI
binary (`ccam` -> `agenthub`), the env var prefix (`CCAM_` ->
`AGENTHUB_`), the Prometheus metric namespace (`ccam_*` ->
`agenthub_*`), the tmux session prefix (`ccam-lane-<id>` ->
`agenthub-lane-<id>`), the per-repo runtime profile directory
(`.ccam/profile` -> `.agenthub/profile`), the lanes state root
(`~/.claude/ccam-lanes` -> `~/.claude/agenthub-lanes`), the bundled
plugins (`plugins/ccam*` -> `plugins/agenthub*`) and their slash
commands (`/ccam-doctor` -> `/agenthub-doctor`, `/ccam:*` ->
`/agenthub:*`).

Because there is no alias, an existing install has to be updated by
hand: rename its `.ccam/profile` directory and any `CCAM_*` variables,
and reinstall the plugin under its new name.

Two other name families are deliberately left alone here, since they are
not just strings: the `Claude-Code-Monitor` repository/marketplace name,
and the `agent-dashboard` npm package plus its `~/.claude/agent-dashboard`
runtime directory, which holds the live database and needs a migration
rather than a rename.

Verified: server 1406/1406, client 459/459, `grep -i ccam` clean across
tracked files, `openapi.yaml` regenerated (95 paths, unchanged count).

plugins/agenthub-cost-guard/commands/forecast.md

@@ -0,0 +1,27 @@
+---
+description: Quick month-end spend projection from the daily trend
+argument-hint: "[week|month]"
+---
+
+Give a quick spend projection for the end of the **$ARGUMENTS** period (`week` or
+`month`; default `month` if empty).
+
+1. Fetch the trend and current spend in parallel:
+   ```
+   curl -s http://localhost:4820/api/analytics
+   curl -s http://localhost:4820/api/pricing/cost
+   ```
+   From `/api/analytics` read `daily_sessions` (`[{ date, count }]`) and the session
+   total; from `/api/pricing/cost` read `total_cost`.
+
+2. Project:
+   - `avg_cost_per_session = total_cost / total_session_count`.
+   - `avg_daily_spend = mean(last 7 days of daily_sessions[].count) × avg_cost_per_session`.
+   - `days_remaining` = days left until end of the chosen period (week → Sunday; month → last calendar day).
+   - `projected_total = total_cost + avg_daily_spend × days_remaining`.
+
+3. Print: spend-to-date, `avg_daily_spend`, `days_remaining`, and the **projected end-of-period total** (USD, 4 decimals), with a ▲/▼ note on whether the 7-day pace is above or below the trailing 14-day pace.
+
+State that daily spend is approximated from session counts. If the dashboard is
+unreachable, tell the user to start it with `npm start` from the repo root. Keep it to
+a few lines. Read-only — do not modify anything.