agnostic guard: compound provider words, source symlinks, and RFC tool names (#417 follow-up) #419

Three P2 findings from Codex's last pass on #417 (01a39b3, the agnosticism guard src/agnostic_guard_test.zig on development), after that PR had used its three review-fix rounds.

1. Compound and package forms (around line 308). Steamworks and libsdl2-dev tokenize as Steamworks / libsdl2; CamelCase splitting doesn't extract steam, and numeric-root classification reduces the latter only to libsdl. Add the known compound/package forms (steamworks, libsdl, libsdl2, …) or recognise conventional affixes (lib prefix, works/sdk/dev suffixes) before classifying.
2. Source symlinks (around line 526). Where the walker reports .sym_link, a committed link such as src/cli/steam.zig is skipped, so both its forbidden path and its target's contents bypass the guard. Either follow source-shaped links safely (stat the target, scan it, still path-check the link name) or fail on encountering one.
3. Provider tool and SDK names from the RFC (around line 42). The RFC assigns butler to the itch provider and UIKit glue to the iOS provider, but neither butler nor uikit is forbidden. Add the tool/SDK identities the RFC enumerates (butler, uikit, steamworks, steamcmd, xcodebuild, adb, emcc, …) and recompute the allowlist.

Each needs a self-test that asserts the mechanism (an ASCII twin passes) in the existing style.

Part of #406 (enforcement).

https://claude.ai/code/session_01R2K5sJDL5Msn1uRTkybiDP