Changelog

0.1.6

foil:namespaces/0 returns {ok, [namespace()]} — the list of registered namespaces. Saves callers from having to peek at foil_modules:lookup/1 internals to enumerate state.
README gained a "Performance characteristics" section spelling out the compile-cost vs. lookup-cost trade-off (foil's load/1 is O(n); lookup/2 beats ETS at ~0.1 μs vs 0.4 μs for *_direct_* patterns). Helps callers pick foil vs. ETS for new use cases.

B4's "fix foil_compiler:load/2 spec to propagate compile_failed" recommendation was checked on inspection and not acted on: compile:forms/2 can only fail when the forms produced by foil_compiler:forms/2 are malformed, which is a foil internal bug rather than a runtime user-facing error. The current {ok, Module, Bin} = compile:forms(...) badmatch crashes loudly on that path, which is the right behaviour. Surfacing it as {error, compile_failed} would force every caller to write a branch they can't sensibly handle.

foil_compiler:to_syntax/1 now accepts maps, references, pids, ports, funs, and non-byte-aligned bitstrings. Maps compile to a proper map_expr literal. The rest have no abstract literal form, so they ride through an integer syntax node — the BEAM module loader carries them in the compiled module's constant pool as-is, and foil:lookup/2 returns them unchanged.
eunit case non_literal_terms_test round-trips each new type (including a nested tuple/map combination that mixes literal and non-literal values).

CI moved from Travis (decommissioned years ago) to GitHub Actions. Matrix now covers OTP 25, 26, 27, 28.
Documentation migrated from edown to rebar3_ex_doc. Generated doc/ directory removed; HTML docs are now published to hexdocs.
Bumped metal dependency from 0.1.1 to 0.1.2.
Tightened the error/0 type from {error, atom()} to a sum: {error, foil_not_started | key_not_found | module_exists | module_not_found}. Dialyzer-checkable; same atoms the code already returns. No behavioural change.
foil.erl refactored to dispatch through a ?WITH_MODULE(...) macro (defined in foil.hrl). Removes ~40 lines of repeated try/catch scaffolding from all/1, delete/1, delete/2, insert/3, load/1, and lookup/2. Macro rather than function so the cache hot path stays branch-only; bench numbers unchanged.

.travis.yml, elvis.config, bin/elvis, rebar.config.script (rebar2 compatibility) — all unused.
coveralls plugin and Makefile target — Travis-specific tooling.
Coveralls and Travis build badges from the README.