fix: resolve failing CI checks - tryCatch handler, top-level return(), flow-typed install

[Copilot]

Three distinct CI failures on main triggered by the shinycoreci scheduled check run.

Fixes

• tryCatch error handler missing condition arg (R/shinyModule.R): error = function() must be error = function(cond) — newer R versions enforce this, causing Error in value[[3L]](cond): unused argument (cond) in test-shiny_module.R:21.

  # Before
  tryCatch({...}, error = function() { FALSE })
  # After
  tryCatch({...}, error = function(cond) { FALSE })

• Top-level return() in example (R/shinyModule.R, man/reactlog_module.Rd): The if (!require("shiny")) { return() } guard fails with no function to return from when executed at the top level (exposed by the check-depends-only job which omits Suggests). Replaced with the if (require("shiny")) { ... } pattern.

• flow-typed install breaking yarn install (bin/postinstall.sh): flow-typed install fetches from GitHub at install time and was exiting 1 with UNCAUGHT ERROR: [{}, ...], failing the entire yarn install --immutable step. Made non-fatal with || true.

Note: The macOS-latest (4.6.0) failure (HTTP 404 on R download) is external — R 4.6.0 binaries were not yet available at run time and is not addressable in this repo.