Build an isolated ARMv7 Termux package

[isomorphisms]

What this does

• builds the code/ tree natively in TUR's 32-bit Android arm environment on an ARM runner
• publishes an installable ir_*.deb, checksum, source/build record, and exact build-environment package list
• installs the runtime privately under $PREFIX/lib/ir/R and exposes only ir and irscript, leaving ordinary R untouched
• keeps the phone package lean by disabling X11, Tcl/Tk, Java, and the recommended-package bundle
• pins the TUR, termux-packages, checkout-action, and artifact-action revisions

Acceptance

The job fails unless the package is arm, its runtime is ELF32 ARM, R/Rscript are absent, and this executes successfully in the ARM Termux environment:

x ← 8 ÷ 2
stopifnot((x = 4))

A successful job is strong build and container execution evidence. Installation and execution on the actual ARMv7 Android Go phone remains a separate final acceptance step.