fix: Tectonic sanitizer regex must require uppercase after fa

The fa-strip regex matched familydefault, fancyhf, fancyfoot (all begin
with fa), corrupting the preamble and causing a Missing begin-document
error (the next failure after the segfault was fixed). fontawesome icons
are fa + UPPERCASE, so the regex now requires an uppercase letter.
Regenerated the sanitized warmup asset; verified familydefault, fancyhf,
fancyfoot and begin-document survive while faPhone and fontawesome5 are
removed. Tests 11/11.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

assets/default_resume.tectonic.tex

@@ -49,14 +49,14 @@
 
 % custom font: helvetica-style (tgheros substituted with helvet)
 \usepackage{helvet}
-\renewcommand*{\sfdefault}
+\renewcommand*\familydefault{\sfdefault}
 %% Only if the base font of the document is to be sans serif
 \usepackage[T1]{fontenc}
 
 
 \pagestyle{fancy}
-{} % clear all header and footer fields
-{}
+\fancyhf{} % clear all header and footer fields
+\fancyfoot{}
 \renewcommand{\headrulewidth}{0pt}
 \renewcommand{\footrulewidth}{0pt}
 

src/latex_resume.py

@@ -615,7 +615,13 @@ def ensure_compilable_document(src: str) -> str:
 # full TeXLive handles it; Tectonic crashes. We therefore strip the OTF/exotic-font
 # loaders from the COMPILED copy only. The downloadable `.tex` (report["tex"]) keeps
 # the full design so the user still gets icons + FiraMono in Overleaf.
-_FA_CMD_RE = re.compile(r"\\fa[A-Za-z]+\*?")
+#
+# fontawesome icon commands are `\fa` + an UPPERCASE letter (camelCase): \faPhone,
+# \faEnvelope, \faGlobe, \faRupeeSign. The uppercase requirement is CRITICAL so we
+# DON'T also eat lowercase `\fa…` macros that the template needs —
+# `\familydefault`, `\fancyhf`, `\fancyfoot` — which would corrupt the preamble and
+# cause "Missing \begin{document}".
+_FA_CMD_RE = re.compile(r"\\fa[A-Z][A-Za-z]*\*?")
 
 
 def _sanitize_for_tectonic(src: str) -> str: