#11158: doctor: warn when system RAM is at or below 2 GB (deafult in the most cloud platform)

**Title:** Doctor: warn when system RAM is at or below 2 GB --- #### Summary Add a low-memory warning to `openclaw doctor` that fires when total system RAM is 2 GB or less. Many cheap cloud VMs (default tier on most providers) ship with only 2 GB, and running `doctor` or other heavy operations on them can OOM the process silently. This surfaces the problem early and suggests adding swap. #### Use Cases - Users deploying OpenClaw on budget cloud VMs (Vultr, DigitalOcean, Hetzner, etc.) with 2 GB RAM hit OOM during `openclaw doctor` with no prior warning. - The warning appears at the top of the doctor output so users see it before any heavy checks run. #### Behavior Changes - `openclaw doctor` now calls `noteLowMemoryWarning()` early in its flow (before config loading and gateway health checks). - On systems with total RAM <= 2 GB, a "Low memory" note is printed with the detected RAM, the 2048 MB threshold, and a `fallocate` swap command. - On systems with > 2 GB RAM, no output change. #### Codebase and GitHub Search - [x] Searched codebase for existing memory/RAM checks: none found (`os.totalmem` unused prior to this PR). - [x] Searched GitHub issues for "OOM", "low memory", "doctor memory": no existing issue. #### Tests - `doctor-platform-notes.low-memory.test.ts` (3 tests, all passing): - Warns at exactly 2 GB (boundary) - Warns at 512 MB (well below threshold) - Silent at 4 GB (above threshold) ``` pnpm test -- --run src/commands/doctor-platform-notes.low-memory.test.ts ✓ src/commands/doctor-platform-notes.low-memory.test.ts (3 tests) 9ms Test Files 1 passed (1) Tests 3 passed (3) ``` #### Manual Testing N/A (unit-tested with dependency injection; `os.totalmem()` is injected via `deps.totalMemBytes`). <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR adds a new platform note for `openclaw doctor` that warns when the machine has <= 2 GB of total system RAM. The warning is implemented as `noteLowMemoryWarning()` in `src/commands/doctor-platform-notes.ts` (using `os.totalmem()` by default, with dependency injection for tests), invoked early in `doctorCommand` before heavier checks run. It also adds a Vitest unit test suite covering the boundary and above/below-threshold behavior, and records the feature in the changelog. <h3>Confidence Score: 3/5</h3> - This PR is close to mergeable but has a robustness concern in the early doctor flow. - The change is small and well-tested for normal paths, but the new early `os.totalmem()` call is unguarded; if it throws on a platform/host where total memory cannot be queried, it can crash `openclaw doctor` before other checks run. - src/commands/doctor-platform-notes.ts <!-- greptile_other_comments_section --> _{(3/5) Reply to the agent's comments like "Can you suggest a fix for this @greptileai?" or ask follow-up questions!} <!-- /greptile_comment -->