Nepeta mode: purrfect cat-speak reskin (closes #17)

[melogtm]

Summary

This PR adds an opt-in Nepeta mode — a lighthearted easter egg that reskins trigger's own generated output with Nepeta Leijon's cat-speak quirk from Homestuck. When enabled, the shell prefix message, prompt, help text, and certain builtin error/status messages get cat-faced and pun-translated.

Toggle via env var or builtin:

# Enable at startup
TRIGGER_NEPETA=1 ./cmake-build-debug/shell
# Or toggle during a session
nepeta on
nepeta off
nepeta status
nepeta        # bare = toggle

Scope boundary

Only trigger's own output is affected:

• Prompt changes from > to :33 <
• Startup banner shows a random Nepeta quote
• Help text and certain builtin messages (cd no-args error, exit invalid-code error) pass through pun translation
• External program output, pipeline data, perror()/strerror(), and builtin name listings are never touched

When Nepeta mode is disabled (the default), all output is byte-identical to the previous behavior.

Pun dictionary

Whole-word alpha-run matching with case preservation on first letter:

for→fur, perfect→purrfect, great→clawesome, awesome→pawsome, friend→furriend, now→meow, help→halp

Files changed

File	Change
include/nepeta.h (new)	Header: getter/setter, init-from-env, prompt, banner, translate, say, random_quote
src/nepeta.c (new)	Implementation of pun translation engine and all Nepeta-mode functions
include/builtins.h	Declare trigger_nepeta
src/builtins.c	Add nepeta builtin, route cd/help/exit messages through trigger_nepeta_say
src/main.c	Use trigger_nepeta_prompt(), call init_from_env + print_banner at startup
CMakeLists.txt	Add nepeta.c/nepeta.h, new test_nepeta target
tests/test_nepeta.c (new)	18 tests: state, prompt, translate, say capture, random quote, env init
tests/test_builtins.c	Bump count to 8, add nepeta find+fn-pointer check, 5 dispatch tests

Closes #17

[Copilot]

Pull request overview

This PR introduces an opt-in “Nepeta mode” easter egg that reskins Trigger’s own generated output (prompt/banner/help and selected builtin messages) using a cat-speak/pun translation layer, while keeping normal behavior unchanged when disabled.

Changes:

• Added a new Nepeta module (nepeta.h / nepeta.c) implementing enable/disable state, prompt/banner output, and word-level translation.
• Added a new nepeta builtin and routed some builtin output through the Nepeta “say” helper.
• Added a dedicated Nepeta test suite and extended builtin tests; integrated the new module and tests into CMake/CTest.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/test_nepeta.c	New module-level tests for Nepeta enable state, prompt, translation, say, quotes, and env init.
tests/test_builtins.c	Adds coverage for the new nepeta builtin and updates builtin count/lookup assertions.
src/nepeta.c	Implements Nepeta state, translation engine, prompt/banner, and random quotes.
src/main.c	Initializes Nepeta from env and switches prompt rendering to Nepeta-aware prompt helper.
src/builtins.c	Registers nepeta builtin and routes selected builtin output through Nepeta-aware output.
include/nepeta.h	New public header for Nepeta APIs.
include/builtins.h	Declares the new trigger_nepeta builtin function.
CMakeLists.txt	Adds src/nepeta.c / include/nepeta.h and introduces test_nepeta in the test target list.

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[DuAlmeida995]