feat(tools): add host doctor, crash report and frame-pacing baseline

Turns "it does not work" into an attachable report instead of a log-less
issue. Three read-only host tools, reachable from the launcher:

- doctor.py checks GPU/driver, Vulkan ICDs, display session, memory, disk,
  overlay layer, core-dump limit, i915 panel self-refresh and prefix/runtime
  state. --json and --report produce an issue attachment; warnings do not fail.
- crash-report.py bundles the doctor checks, process table, dserver and
  launcher log tails, graphics kernel messages, display state and recent core
  dumps. Environment is never collected and home/user/host are redacted.
- perf-baseline.py parses the game's own netstats.csv into average FPS,
  p50/p95/p99 frame time, slowest-quarter FPS and hitch count, with --json and
  --append for before/after comparisons.

COMPATIBILITY.md records the verified UHD 620 row with measured numbers
(24-32 avg FPS, p99 44-98 ms) and explains how to submit another one.

docs/COMPATIBILITY.md

@@ -0,0 +1,83 @@
+# Compatibility matrix
+
+This page answers one question: **on which machines has darling-lol actually
+been used to play, and what did it run like?**
+
+It is a record of real reports, not a list of every configuration that might
+work. "Verified" below means the Riot Client opened, League launched, a match
+was played manually, and the store was reachable. Experimental or untested
+hardware is not listed until someone sends a report.
+
+The project is unofficial and carries account risk. Never test on an account you
+care about, and never play ranked while testing (see the warning in the
+[README](../README.md)).
+
+## How to add a row
+
+Run these on the machine you played on, after a match:
+
+```sh
+darling-lol --doctor                 # host, GPU, Vulkan, session, prefix checks
+darling-lol --doctor --report doctor.json   # same checks as a JSON attachment
+darling-lol --perf                   # frame pacing from the game's own logs
+darling-lol --perf --json            # the same numbers as JSON
+```
+
+`lol doctor` needs no runtime and starts nothing, so it is safe to run at any
+time. `lol perf` reads the `netstats.csv` files that League already writes; it
+does not touch the client or the game.
+
+Open an issue titled `Compatibility: <distro> / <GPU>` and attach `doctor.json`
+plus the `perf --json` output. Do not paste a full `~/.darling` log or your home
+directory; `lol report` produces a redacted bundle if more diagnostics are
+needed. Then add a row here in a pull request, or mention the issue and a
+maintainer will add it.
+
+### What the numbers mean
+
+- `avgfps` is the mean of League's own ten-second `game.frametime_average`
+  samples over the whole match.
+- `p50/p95/p99ms` are frame times: the typical frame, the slow 5 %, and the
+  slowest 1 %.
+- `slowfps` is the average FPS over the slowest quarter of the match, which is
+  closer to what stutter feels like than the headline average.
+- `hitch` counts ten-second samples whose frame time is at least twice the
+  match median.
+- FPS depends on map, graphics settings, charger/power state, other programs and
+  shader-cache warmth. Treat comparisons as useful only when those match.
+
+## Verified configurations
+
+| Distro / desktop | CPU / GPU | Driver | Session | Kernel | Runtime | Result | Frame pacing |
+|---|---|---|---|---|---|---|---|
+| Omarchy (Arch), Hyprland | Intel i5-10210U / Intel UHD 620 | `i915`, Mesa ANV | Wayland + Xwayland | 7.2.5 | patched Darling, `-O2` libc/libc++ | Client, game, ARAM/Swiftplay and store work; playable at low settings | 24–32 avg FPS over five ARAM matches; p99 44–98 ms; slowest quarter 20–27 FPS |
+
+Notes for the UHD 620 row:
+
+- Measured 2026-10-23 with `tools/perf-baseline.py` on five match logs, no
+  FPS overlay. The laptop has 11.5 GiB RAM and a 15 W Comet Lake CPU.
+- The 24 FPS match is also the longest log and the one with the most samples;
+  the spread between matches is larger than the difference between recent
+  builds, so single-match comparisons are not meaningful.
+- Intel panel self-refresh (`i915.enable_psr`) was on for part of this period.
+  See [panel self-refresh](TROUBLESHOOTING.md#blocky-video-or-flickering-startup-logo).
+- Expect first-match shader compilation to show up as a low `p99` until the
+  cache is warm.
+
+The Ryzen 5 5500 / RX 6600 development machine is faster and is documented
+separately in [status](STATUS.md#game-fps-2026-10-1314). It is not a laptop
+baseline and should not be read as the expected result on integrated graphics.
+
+## Not verified
+
+These are common laptop configurations without a confirmed play test here.
+Reports are welcome, but treat them as unknown rather than supported:
+
+- Recent AMD integrated graphics (Radeon 680M/780M) under RADV.
+- NVIDIA hybrid laptops using PRIME render offload.
+- Fedora Silverblue and other immutable distributions with Nix.
+- Intel Arc discrete GPUs.
+
+Known driver caveats live in the
+[troubleshooting guide](TROUBLESHOOTING.md#nvidia) and
+[hybrid graphics notes](TROUBLESHOOTING.md#hybrid-graphics-laptops-amdintel-igpu--nvidia).

docs/TROUBLESHOOTING.md

@@ -1,5 +1,31 @@
 # Troubleshooting
 
+## Before reporting a problem
+
+Run the host checks first; they start nothing and work while a client is open:
+
+```sh
+darling-lol --doctor
+```
+
+It reports the GPU/driver, Vulkan, display session, memory, disk, overlay layer
+and prefix state, and ends with the checks that need attention. If you open an
+issue, attach the machine-readable report and a crash bundle instead of a
+hand-copied log:
+
+```sh
+darling-lol --doctor --report doctor.json
+darling-lol --report                # ~/.cache/darling-lol/reports/*.tar.gz
+darling-lol --perf                  # frame pacing from the game's own logs
+```
+
+The crash bundle contains the doctor checks, the process table, the runtime and
+launcher log tails, graphics kernel messages, display state and recent core
+dumps. It does not collect environment variables, tokens or passwords, and it
+replaces your home directory, user name and host name with placeholders unless
+you pass `--no-redact`. See [compatibility](COMPATIBILITY.md) for what the
+performance numbers mean and for verified machines.
+
 ## NixOS launcher fails before Riot opens
 
 A message saying Darling must be setuid root is not fixed by running `sudo`