Add experimental Scala 3 source scanner

[aboisvert]

Adds an experimental Scala 3 scanner using Scalameta 4.17.3. Groma reads its selected .scala files using a bundled parser and Java runtime, without installed Java, Scala, sbt, project dependencies, or a project build.

The scanner reports declarations, source outlines, operations, and call-site evidence at original source locations. Extension methods keep their enclosing scope: top-level functions or members of the declaring type/object. Calls remain unresolved when syntax cannot prove their target. A parse/read error rejects the whole scan; the scanner does not skip failing files or emit duplicate-body fingerprints.

Source selection uses Groma's existing include/exclude lists, including custom source paths. Includes discovery, the existing five-host package assembly flow, upstream license notices, documentation, and a curated scanner component. The branch includes main through 0a75d08d, including the COBOL/NASM additions.

Task: TASK-549 — Align the Scala scanner PR with current scanner contracts.

Validation:

• bun run check: 781 passed, 51 existing optional skips, no failures.
• Isolated Scala package checks: 34 assertions, including extension ownership, visibility, source locations, calls and the polymorphic colon argument.
• Relocated package test: 7 assertions, empty home, no installed language tools.
• Five-host package assembly checks pass. Cold simplicity, implementer specification/quality, and final full-context complexity reviews pass.

Real-project checks used the packaged scanner on macOS ARM64 with default source selection, empty homes and no language tools on PATH. All three pass scans, outlines, exact file inventory, repeated-observation equality and source-position consistency; all checkouts remain unchanged and clean.

Project and revision	Selected files	Result
Ox, Scala 3.3.8	214	Pass; previously missing extension methods are present.
Neotype, Scala 3.3.8	188	Pass; the top-level unwrap extension is present.
Kyo, default Scala 3.9.0	4,307	Pass; the polymorphic argument parses, with its method and calls at original locations.

The audit exposed omitted extension groups and a parser failure in Kyo. Commit 20668945 fixes both and adds small regression fixtures; the same repository revisions were rerun without excluding the failing source.

Platform CI for the fix commit passed on Linux, macOS, and Windows: run 37441097162. The earlier implementation passed Linux, macOS, and Windows CI. Architecture comparison is separately blocked before scanning by the repository's actions/checkout fork restriction in pull_request_target; no unsafe-checkout override was added.

Merged as 4e984291d1478154e0f0bd974bfb7c2d81bbdce8. The five-platform package preparation run passed on that merged commit, including every host build and fresh-checkout check. Publishing jobs were skipped. The assembled npm tarball passed an offline npm install, the installed-package test without language tools, and npm publication dry run. The new npm package is @groma/scanner-scala@0.1.0; the complete 105.4 MB tarball is prepared and awaits owner login/approval for the first npm publication.

[github-actions]

Groma architecture comparison

Changes	Added	Modified	Removed
Components	1	1	0
Relationships	0	0	0

Open before / after comparison

Compared 0a75d08 (merge base) → 9797641.

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