Release/v0.3

[dannymeijer]

Release 0.3

This PR promotes release/v0.3 into main. It contains the 0.3 language, stdlib, tooling, documentation, and stabilization work accumulated since the 0.2 release line.

The full user-facing release narrative lives in Release 0.3. This PR body is intentionally a reviewer-facing summary.

Highlights

• Language surface: precise numeric annotations, loop: expressions with break <value>, if let / while let, union narrowing, value enums, enum-owned methods, enum trait adoption, Rust trait adoption from Incan source, trait-based operator overloading, and protocol hooks for core syntax.
• Generated Rust and ownership: ownership/coercion emission now flows through an explicit argument-passing plan, reducing the previous duckborrower drift where local call emitters made competing borrow decisions.
• Stdlib: new or expanded surfaces for std.collections, OrdinalMap, std.graph, std.datetime, std.encoding, std.hash, std.compression, std.regex, std.json, std.logging, temporary filesystem helpers, iterator adapters, and Result combinators.
• Tooling and tests: deterministic incan.lock files, the RFC 053 formatter spacing contract, inline tests, fixtures, async fixtures, first-class test-runner behavior, generated reports, and faster release-gate organization.
• Package/import-boundary hardening: fixes for decorator metadata, partial presets, public aliases, static imports, inline test batching, dependency-scoped script builds, generated helper qualification, and imported static initialization cycles.
• Docs and RFCs: release notes, updated language/reference/how-to docs, RFC lifecycle cleanup, modernized RFC frontmatter, and documented known limitations.

Migration Notes

• Ordinary int and float code does not require a source migration; those spellings remain valid and keep their i64 / f64 representations.
• Projects that gate on incan fmt --check should expect one-time formatter diffs from the RFC 053 vertical-spacing contract.
• Projects with local bare type names such as decimal or numeric should rename those local types or use the new parameterized numeric family forms.
• Most language and stdlib additions are additive; known limitations and future follow-ups are documented in the release notes.

Verification

• GitHub Actions CI for current head 6bcec3a1 completed successfully in CI run #860.
• The release branch has repeatedly passed make pre-commit through the stabilization PRs.
• Latest closeout left /Users/danny/Development/encero/incan clean on release/v0.3...origin/release/v0.3.

Release Links

• Release 0.3 notes
• Release 0.2 notes
• Head branch: release/v0.3
• Base branch: main