feat(ui): call lanes "workspaces" in the UI, CLI output and docs

Copy-only rename (workspace redesign, phase 0). The word a user reads
changes — "Lane" → "Workspace", "Add lane" → "Add workspace" — in both
locales, in agenthub CLI prose and help, in the server's error messages
and in the docs. Every identifier stays: /api/lanes, `agenthub lanes`,
--lane, AGENTHUB_LANE_ID, error codes, tmux names, DB tables, file,
component and i18n key names. docs/LANES.md keeps its name, retitled
"Workspaces (lanes)".

docs/DATABASE.md

@@ -211,7 +211,7 @@ CREATE TABLE sessions (
 | `awaiting_reason` | TEXT | YES | Why the row is waiting: `notification`, `stop`, `session_start`, or `interrupted`. Set/cleared in lock-step with `awaiting_input_since` (SessionStart→`session_start`, Stop→`stop`, permission/input Notification→`notification`, watchdog/Esc recovery→`interrupted`). NULL otherwise. Exception: a `compact`-source SessionStart preserves the existing value (neither stamps `session_start` nor clears it) |
 | `transcript_path` | TEXT | YES | Absolute path to the session's JSONL transcript. Written by `routes/hooks.js` on the first event that carries it (subsequent events no-op via a SQL guard) and read by the periodic compaction sweep — so the sweep touches only active session rows instead of scanning the entire `events` table for `json_extract(data,'$.transcript_path')`. Backfilled once from `events` by the `db.js` migration |
 | `source` | TEXT | NO | Data source this session was captured from. `'local'` for this machine's own Claude Code history (the default); otherwise the `remote_sources.id` of the remote SSH machine it was pulled from. Powers the `sources` query filter on `/api/sessions`, `/api/events`, `/api/agents`, `/api/stats`, and `/api/analytics`, and the `sources` facet on `/api/sessions/facets`. Indexed by `idx_sessions_source` |
-| `tool` | TEXT | NO | The AI coding CLI that produced the session. `'claude'` for every hook-created and imported row (the default); `'codex'` for a session ingested from Codex's rollout journals by `server/lib/codex-usage.js` (see `codex_rollouts`) or created by a Codex hook (`tool: "codex"`, `server/lib/codex-hooks.js`) — a Codex session keeps the status its hooks give it while they are current (its newest event at or after its newest journal write minus two minutes); once they stop (removed, untrusted) the journal decides again. A codex row has no `transcript_path`, and, going by the journal, its `status` is `active` only while one of its journals was written in the last two minutes. `'antigravity'` for an agy CLI conversation, ingested by `server/lib/antigravity-usage.js` (see `antigravity_conversations`) or created by an Antigravity hook (`server/lib/antigravity-hooks.js`); no `transcript_path`, and `active` until it has been quiet — no write to its conversation file (or a non-empty `-wal`) or transcript, no hook event — for ten minutes when it has hook events, two minutes when it has none; it then settles to `completed`, its agents too. The startup cleanup of stale `active` sessions and a lane purge touch only the matching tool's rows (a purge takes the sessions of the lane's own `tool`). The Workspace's attach/resume list offers `'claude'` rows only |
+| `tool` | TEXT | NO | The AI coding CLI that produced the session. `'claude'` for every hook-created and imported row (the default); `'codex'` for a session ingested from Codex's rollout journals by `server/lib/codex-usage.js` (see `codex_rollouts`) or created by a Codex hook (`tool: "codex"`, `server/lib/codex-hooks.js`) — a Codex session keeps the status its hooks give it while they are current (its newest event at or after its newest journal write minus two minutes); once they stop (removed, untrusted) the journal decides again. A codex row has no `transcript_path`, and, going by the journal, its `status` is `active` only while one of its journals was written in the last two minutes. `'antigravity'` for an agy CLI conversation, ingested by `server/lib/antigravity-usage.js` (see `antigravity_conversations`) or created by an Antigravity hook (`server/lib/antigravity-hooks.js`); no `transcript_path`, and `active` until it has been quiet — no write to its conversation file (or a non-empty `-wal`) or transcript, no hook event — for ten minutes when it has hook events, two minutes when it has none; it then settles to `completed`, its agents too. The startup cleanup of stale `active` sessions and a workspace purge touch only the matching tool's rows (a purge takes the sessions of the workspace's own `tool`). The Workspace's attach/resume list offers `'claude'` rows only |
 
 **Constraints:**
 - `status` must be one of the four enum values