feat: bundle Linear issues, harden path boundaries

[koistya]

Adds Linear as a bundle source, and hardens the path handling around it after a pre-release audit turned up five ways a bundling run could read or delete the wrong thing.

Linear issues as virtual files

A bundle can now name linear alongside (or instead of) globs. Each issue becomes a virtual file, so it gets an index entry, a line range, and can be filtered with an ordinary ! exclusion — nothing downstream needs to know it wasn't read off disk.

bundles: {
  planning: { include: ["docs/**"], linear: { team: "ENG", project: "Roadmap" } },
  backlog: { linear: "ENG" },
}

Each source also emits linear/issues.md ahead of the issues: scope heading, a count per workflow state, and a row per issue ordered by number. Without it the index is forty lines of opaque identifiers, and issue numbers sort as text (SM-2 between SM-19 and SM-20). Drop it with !linear/issues.md.

team is required: a workspace-wide fetch looks innocuous and can pull thousands of issues into a context window. Auth reads LINEAR_API_KEY from the environment rather than config, because config files get committed. Pagination orders by createdAt — the updatedAt default is mutable, so an issue edited mid-run reorders the list under the cursor and drops or repeats its neighbours.

Path boundaries

Five defects, one cause: paths were compared as the strings that name them, and filters were treated as best-effort. That's fine for deciding what goes into a bundle and wrong for deciding what gets deleted — and .gitignore had quietly become the second kind, because the docs promise it keeps secrets out.

Defect	Fix
outDir: "src" deleted the sources it was asked to bundle	Automatic emptying only for the conventional .srcpack
A symlinked .srcpack emptied and wrote into its target	Ownership decided on the physical path; a redirected .srcpack fails the run
A symlinked directory was walked and everything under it bundled	Globs no longer follow symlinks at any level
Nested .gitignore files were never read	Resolved per directory, deepest rule first, no re-inclusion under an ignored directory
--no-uplaod uploaded	Unknown flags, unknown config keys, and upload.exclude entries naming no bundle are errors

Two related holes: two bundles could resolve to one physical file through a symlink or a case/normalisation alias, and a bundle could swallow its own previous output when reached by a different spelling.

Comparison identity is now NFC-normalised and case folded on every platform — a filesystem that folds either one turns two bundles into a silent overwrite, and a config that works in CI but loses a bundle on a laptop is worse than one rejected everywhere. Ownership deliberately stays an exact match, since folding there could only widen what gets deleted.

Writes go through a temp file and rename, so a symlink sitting at the output path is replaced rather than written through, and each bundle appears whole or not at all.

Full rationale in ADR 003 and ADR 004, both added here.

Breaking change

A custom outDir is no longer emptied automatically — set emptyOutDir: true to keep the old behaviour. Stale files are a nuisance; deleted sources are not, and 0.x is the time to take that break. Version bumped to 0.3.0.

Verification

Each defect was reproduced against the built CLI before being fixed, and every fix is mutation-tested: reverting it alone fails its own regression test. That covers symlink following, nested .gitignore, outDir ownership, lexical vs physical output identity, NFC and case folding, unknown-flag rejection, collision detection, and temp-file writes.

Ran bun test, bun run check, prettier --check, and the VitePress build. Layered .gitignore resolution was cross-checked against git check-ignore, and orderBy: createdAt against the live Linear API.