charts: bundle Inter font + cache-bust README images

Font: the CI runner has neither Inter nor a 'medium' weight, so charts
silently fell back to DejaVu and dropped the medium weight. Ship Inter's
static TTFs (Regular/Medium/SemiBold/Bold, OFL) in assets/fonts/ and
register them via font_manager.addfont(), so every render — laptop or CI
— is byte-for-byte the same house font, no system dependency.

Images: GitHub proxies README images through its camo cache keyed on the
URL, so a stable png path serves a stale image long after the table (plain
markdown) refreshed. Append a per-render ?v=<stamp> to each chart <img>
so the URL changes each render and the image updates in lockstep.

Author: MattJackson

assets/fonts/Inter-Bold.ttf

@@ -0,0 +1,92 @@
+Copyright (c) 2016 The Inter Project Authors (https://github.com/rsms/inter)
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+http://scripts.sil.org/OFL
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded,
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION AND CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.

assets/fonts/Inter-LICENSE.txt

@@ -23,7 +23,13 @@
 
 # When this render happened (UTC). Stamped into every report page + chart footer so a re-run always
 # refreshes and re-commits ALL readmes and ALL images, even when the underlying numbers didn't change.
-RENDER_TS = datetime.now(timezone.utc).strftime("%Y-%m-%d %H:%M UTC")
+_NOW = datetime.now(timezone.utc)
+RENDER_TS = _NOW.strftime("%Y-%m-%d %H:%M UTC")
+# Cache-buster appended to every chart <img> URL in the report. GitHub proxies README images through
+# its camo cache keyed on the full URL — a stable path serves a STALE png long after the table (plain
+# markdown) has updated. A per-render query string changes the URL each time, so the image refreshes
+# in lockstep with the numbers. (Costs nothing; the file on disk is unchanged.)
+CACHE_BUSTER = _NOW.strftime("%Y%m%d%H%M")
 
 # matplotlib is imported lazily (in render) so the report pages can be generated with plain JSON even
 # where matplotlib isn't installed. plt is filled in by _mpl().
@@ -57,10 +63,22 @@ def _mpl():
         import matplotlib.pyplot as _plt
     except ImportError:
         return None
-    for _f in ("Inter", "Helvetica Neue", "Arial", "DejaVu Sans"):
-        if any(_f.lower() in f.name.lower() for f in fm.fontManager.ttflist):
-            _plt.rcParams["font.family"] = _f
-            break
+    # Inter is BUNDLED in the repo (assets/fonts/) and registered here, so the charts render
+    # identically on any machine — a dev laptop, CI, whatever — regardless of what fonts the OS has.
+    # (CI runners have neither Inter nor a "medium" weight, so relying on system fonts silently fell
+    # back to DejaVu and dropped the medium weight. Registering our own TTFs removes that dependency.)
+    fonts_dir = ROOT / "assets" / "fonts"
+    have_inter = False
+    for ttf in sorted(fonts_dir.glob("Inter-*.ttf")):
+        fm.fontManager.addfont(str(ttf))
+        have_inter = True
+    if have_inter:
+        _plt.rcParams["font.family"] = "Inter"
+    else:  # no bundled fonts (shouldn't happen in-repo) — fall back to something always present
+        for _f in ("Helvetica Neue", "Arial", "DejaVu Sans"):
+            if any(_f.lower() in f.name.lower() for f in fm.fontManager.ttflist):
+                _plt.rcParams["font.family"] = _f
+                break
     _plt.rcParams.update({"axes.edgecolor": "#d7dae0", "svg.fonttype": "none"})
     plt = _plt
     return plt
@@ -504,7 +522,7 @@ def rps_cell(val, bound, served):
     for c in charts:
         png = f"{chart_prefix}{c}"  # top5 report points at its own top5_*.png set
         if (RESULTS / f"{png}.png").exists():
-            lines.append(f"![{c}](../../{png}.png)")
+            lines.append(f"![{c}](../../{png}.png?v={CACHE_BUSTER})")
             lines.append("")
     lines.append("---")
     lines.append("Method: added latency = gateway p99 − direct-to-mock p99 at concurrency 1; RPS "