Modernise messaging infrastructure with cli support

Rewrites message_(), warning_(), stop_() to use cli::cli_inform(),
cli::cli_warn(), and cli::cli_abort() when the cli package is available,
with a fully functional plain-text fallback for environments without cli.

Key changes:
- New cli_to_plain() helper converts cli inline markup ({.fun}, {.arg},
  {.val}, {.field}, {.cls}, {.pkg}, {.href}, {.url}, etc.) to readable
  plain-text equivalents for the non-cli fallback path
- word_wrap() simplified: drops add_fn, ANSI re-index algorithm, RStudio
  link injection, and operator spacing hack; returns pasted input unchanged
  when cli is available
- stop_() no longer references AMR_env$cli_abort; uses pkg_is_available()
  directly; passes sys.call() objects to cli::cli_abort() call= argument
- Removed add_fn parameter from message_(), warning_(), and word_wrap()
- All call sites across R/ updated: add_fn arguments removed, some paste0-
  based string construction converted to cli glue syntax ({.fun as.mo},
  {.arg col_mo}, {n} results, etc.)
- cli already listed in Suggests; no DESCRIPTION dependency changes needed

https://claude.ai/code/session_01XHWLohiSTdZvCutwD7ag2b

NEWS.md

@@ -1,3 +1,11 @@
+# AMR 3.0.1.9036
+
+### Updates
+* Modernised messaging infrastructure: `message_()`, `warning_()`, and `stop_()` now use `cli` for rich formatting (colours, inline markup, hyperlinks) when the `cli` package is installed, with a fully functional plain-text fallback when `cli` is absent
+* Removed `add_fn` parameter from `message_()`, `warning_()`, and `word_wrap()` — styling is now handled by `cli` markup or dropped from the plain-text path
+* New internal helper `cli_to_plain()` converts cli inline markup (`{.fun}`, `{.arg}`, `{.val}`, etc.) to plain-text equivalents for the non-cli fallback path
+* Call sites across all R source files updated from `paste0()`-based string construction to cli glue syntax (e.g. `{.fun as.mo}`, `{.arg col_mo}`, `{n} results`)
+
 # AMR 3.0.1.9035
 
 ### New