fix: restate workspace @metamask/* paths per package with local baseUrl

[ulissesferreira]

Explanation

Status: working ✅ — same verification as #167 (builds, tsc --noEmit, traceResolution, full bitcoin-wallet-snap build + snaps-jest run), confirming the per-package restated mapping resolves correctly.

Alternative to #167, built on top of its branch, for side-by-side comparison.

• Keeps fix: resolve workspace MetaMask packages from the monorepo root #167's underlying fix (workspace @metamask/* imports resolve to sibling src, falling back to node_modules when no local src exists) but changes the ergonomics: instead of anchoring paths once at the shared root config, each package sets its own "baseUrl": "./".
• Each package (bitcoin-wallet-snap, tron-wallet-snap, stellar-wallet-snap, sample-snap, snap-networks-utils) restates the @metamask/* (and, where needed, @metamask/snap-networks-utils/* subpath) mapping relative to its own baseUrl, since TypeScript resolves inherited paths against whichever baseUrl is present in the final merged config — not the file that declared paths.
• Preserves baseUrl-relative import ergonomics (e.g. from 'src/entities'), already used in solana-wallet-snap's tests, for every package rather than just one.
• Verified empirically with tsc --traceResolution that setting baseUrl per package without restating the mapping silently breaks workspace-source resolution (falls through to published dist/ in node_modules) — restating it is what fixes that.
• Trade-off vs fix: resolve workspace MetaMask packages from the monorepo root #167: every current and future package with workspace imports needs this mapping restated in its own tsconfig.json, rather than defined once in a shared root config, in exchange for per-package baseUrl ergonomics.

Pros and Cons

Pros:

• Every package keeps baseUrl-relative import ergonomics, which the team explicitly prefers.
• Fix is co-located with the config that uses it — easier to understand a single package's resolution behavior by reading just its own tsconfig.json, no cross-file inheritance reasoning needed.
• Same verified correctness as fix: resolve workspace MetaMask packages from the monorepo root #167 (identical underlying resolution rule).

Cons:

• Duplication: the @metamask/* (and subpath) mapping must be repeated in every package, and in every future package with workspace imports — higher risk of drift/typos, and a maintenance tax that scales with the number of packages.
• Easy to introduce a subtle bug: setting baseUrl without restating the mapping silently reverts to node_modules/dist resolution — confirmed empirically, so this is a real footgun for anyone adding a package who copies baseUrl but forgets the paths block.
• Same inherited config-removal caveat as fix: resolve workspace MetaMask packages from the monorepo root #167, since it's built on that branch.

Clean-install verification

Re-verified from a genuinely fresh worktree — no node_modules, no packages/*/dist anywhere — with only yarn install run (no yarn build):

• yarn lint: passes (exit 0) — ESLint, Prettier, constraints, dependencies, README check all clean.
• Raw tsc --noEmit per package (bypassing the root typecheck script's own pre-build step, to test resolution with zero builds anywhere): all 6 workspaces pass with 0 errors, correctly resolving @metamask/* (including the snap-networks-utils/* subpath) straight from src/ per package's own restated baseUrl-relative mapping.
• stellar-wallet-snap couldn't run via yarn workspaces foreach ... exec tsc (command not found: tsc) — pre-existing gap: that package's package.json has no typescript devDependency, unrelated to this PR. Running tsc directly against it passes with 0 errors.

Confirms the fix holds in the worst case (fresh clone, install-only, zero builds), not just when a stale dist/ happens to already exist.

References

• Alternative to fix: resolve workspace MetaMask packages from the monorepo root #167
• Compared side-by-side with fix: resolve workspace MetaMask packages from the monorepo root #167 (root-anchored, no per-package baseUrl) and fix: add TypeScript project references, mirroring MetaMask/core #170 (references-only, does not fix resolution)

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them