Replace PlotKit submodule with redesigned pure-Python PlotKit (#171)

.gitmodules

@@ -1,3 +1,3 @@
 [submodule "PlotKit"]
 	path = PlotKit
-	url = git@github.com:kandrosov/PlotKit.git
+	url = git@github.com:cms-flaf/PlotKit.git

docs/ci/integration-pipeline.md

@@ -29,9 +29,12 @@ Repos with the trigger enabled: HH_bbtautau, HH_bbWW, H_mumu, FLAF, Corrections,
     ```text
     @cms-flaf-bot please test
     - https://github.com/cms-flaf/FLAF/pull/272
+    - https://github.com/cms-flaf/PlotKit/pull/2
     ```
     Shorthands include `- <repo>_version=PR_<n>`, a `…/pull/<n>` URL, a `…/tree/<branch>` URL, and
-    `- gitlab_branch=<branch>` to run a non-default `flaf_integration` branch.
+    `- gitlab_branch=<branch>` to run a non-default `flaf_integration` branch. `PlotKit_version`
+    pins the `FLAF/PlotKit` sub-sub-module, which is switched after `FLAF` (so it overrides whatever
+    commit the requested `FLAF` pins).
 
 ## `integration_cfg.yaml`
 
@@ -73,7 +76,9 @@ The shared trigger logic distinguishes:
 
 - **root packages** — repos with an `_active` variable (the analyses: HH_bbtautau, HH_bbWW,
   H_mumu);
-- **packages** — repos with a `_version` but no `_active` (FLAF, Corrections, StatInference).
+- **packages** — repos with a `_version` but no `_active` (FLAF, PlotKit, Corrections,
+  StatInference). `PlotKit` is a sub-sub-module (`FLAF/PlotKit`); the build switches it after
+  `FLAF`.
 
 Both may trigger the pipeline; the distinction matters only when editing the trigger logic.
 

docs/concepts/architecture.md

@@ -27,7 +27,7 @@ tools with it. For example, HH→bb̄ττ looks like this:
 ```text
 HH_bbtautau/                  ← the analysis repository (you clone this)
 ├── FLAF/                     ← shared framework (submodule)
-│   ├── PlotKit/              ← plotting helpers (submodule of FLAF)
+│   ├── PlotKit/              ← plotting toolkit: matplotlib/mplhep (+ROOT/cmsstyle); submodule
 │   └── RunKit/               ← workflow utilities (vendored directory, not a submodule)
 ├── Corrections/              ← shared corrections (submodule)
 ├── StatInference/            ← shared stat tooling (submodule; HH analyses only)

docs/glossary.md

@@ -85,7 +85,10 @@ Framework and CMS-computing vocabulary, in plain terms. For the quick on-ramp ve
   testing set; production uses the full model. Defined in `phys_models.yaml`.
 
 **PlotKit**
-: FLAF's plotting-helpers submodule.
+: FLAF's plotting toolkit (a submodule of FLAF, [cms-flaf/PlotKit](https://github.com/cms-flaf/PlotKit)).
+  Renders the stacked CMS plots with **matplotlib + mplhep** by default (no ROOT required) and can
+  optionally render through **ROOT + cmsstyle**. It reads the analysis `config/plot/*.yaml` files and
+  can also run standalone (`python -m PlotKit.cli`).
 
 **Process**
 : A physics object built from one or more datasets (e.g. "TT", "DY", "signal") — what you plot and

docs/reference/tasks.md

@@ -67,10 +67,19 @@ consume.
 - **Parameter:** `--producer-to-aggregate`.
 
 ### `HistPlotTask`
-Produces the final **plots**. **Branches over variables** (one branch per variable).
+Produces the final **plots** via the [PlotKit](https://github.com/cms-flaf/PlotKit) submodule
+(matplotlib + mplhep by default; optional ROOT + cmsstyle). **Branches over variables** (one branch
+per variable).
 
 - **Parameter:** `--variables` (string; restrict which variables).
 
+Plot styling comes from the analysis `config/plot/*.yaml` files (`cms_stacked.yaml`,
+`histograms.yaml`, `<era>.yaml`) — unchanged from the legacy renderer. Signal overlays are scaled by
+`signal_plot_scale` in `global.yaml`: a fixed factor (e.g. `100`) **or** `bkg` to normalise each
+signal's integral to the summed background (shape comparison; the legend then reads
+`… (norm. to bkg)`). PlotKit can also render outside FLAF; see its README for the standalone
+`python -m PlotKit.cli` entry point.
+
 ## Statistical-inference tasks
 
 The limit/fit tasks (e.g. `PlotResonantLimits`, `PlotPullsAndImpacts`) come from the

run_tools/mk_flaf_env.sh

@@ -34,6 +34,7 @@ install() {
     run_cmd pip install bayesian-optimization
     run_cmd pip install yamllint
     run_cmd pip install black
+    run_cmd pip install cmsstyle  # optional PlotKit backend (ROOT/cmsstyle); mplhep comes from LCG
 }
 
 install_gh_cli() {