Your account lists the machine shells you hold, live and recent, and the sessions MCP tool lists them too #10544

Split from #10457 (one list of his sessions).

Done when:

• [x] src/machines/shell.ts exports a plain read of the live sessions for one person: repository, machine, started, last input, last output, peers attached (0 = detached), and the cell's CPU and memory where the cell reports them (a dash where it cannot).
• [x] The account page (src/web/pages/account.ts) has a "Shells" section, one line each, newest first, live ones before the last ended ones (from machine_sessions, with why each ended). It is linked from the command palette as "Your shells". Empty says so in one line.
• [x] The sessions MCP tool takes kind: "shells" with the same rows (no new tool; bun test test/mcp-size.test.ts passes, no ceiling raised).
• [x] Tests: the read returns a live session with real start and last-input times; the page renders it escaped; the MCP kind returns the same rows.

Read only, no buttons yet. bun scripts/design-lint.ts passes; before/after screenshot in the pull.

Reviewed pull #10609 at its head: ticked src/machines/shell.ts exports a plain read of the live sessions for one person: repository, machine, started, last input, last output, peers attached (0 = detached), and the cell's CPU and memory where the cell reports them (a dash where it cannot).; The account page (src/web/pages/account.ts) has a "Shells" section, one line each, newest first, live ones before the last ended ones (from machine_sessions, with why each ended). It is linked from the command palette as "Your shells". Empty says so in one line.; The sessions MCP tool takes kind: "shells" with the same rows (no new tool; bun test test/mcp-size.test.ts passes, no ceiling raised).; Tests: the read returns a live session with real start and last-input times; the page renders it escaped; the MCP kind returns the same rows..