chore(mcp): migrate packages/loopover-mcp from plain .js to real TypeScript

[JSONbored]

Problem (corrected 2026-07-19)

packages/loopover-mcp has 6 plain .js files with no .d.ts declarations at all -- unlike
packages/loopover-miner (which at least has a hand-maintained .d.ts per file, tracked
separately in #7290), this package has zero compiler-verified types on any of its source.

Correction to this issue's original scope: it previously said this was "small enough to be one
reviewable PR." That was wrong -- a real line-count check shows the six files are wildly uneven:

• lib/cli-error.js -- 27 lines
• lib/format-table.js -- 58 lines
• lib/redact-local-path.js -- 58 lines
• lib/telemetry.js -- 68 lines
• lib/local-branch.js -- 592 lines
• bin/loopover-mcp.js -- 6,594 lines

bin/loopover-mcp.js alone is larger than packages/loopover-miner's entire remaining migration
combined. This needs the same phased treatment #7290 already uses, not a single PR.

Proposal

Convert to real .ts source compiled via tsc, mirroring packages/loopover-engine/src/**'s
already-100%-TypeScript precedent. Phased by file size, smallest first:

• Phase 1 (chore(mcp): add tsc build pipeline + convert small lib utilities to TypeScript (Phase 1 of #7291) #7328): build pipeline + the 4 small lib files (27-68 lines each, 211 lines total)
• Phase 2 (chore(mcp): convert lib/local-branch.js to TypeScript (Phase 2 of #7291) #7329): local-branch.js (592 lines -- substantial enough to be its own batch)
• Phase 3 (chore(mcp): convert bin/loopover-mcp.js to TypeScript (Phase 3 of #7291) #7330): bin/loopover-mcp.js (6,594 lines) -- flagged explicitly: whoever picks
  this up should evaluate whether a straight 1:1 rename is even the right move for a file this
  size, versus splitting it into multiple .ts modules as part of the conversion. That's a real
  design decision this issue doesn't make -- it's out of scope to assume either way here.

Deliverables

• Phase 1 (chore(mcp): add tsc build pipeline + convert small lib utilities to TypeScript (Phase 1 of #7291) #7328), Phase 2 (chore(mcp): convert lib/local-branch.js to TypeScript (Phase 2 of #7291) #7329), Phase 3 (chore(mcp): convert bin/loopover-mcp.js to TypeScript (Phase 3 of #7291) #7330) all land
• packages/loopover-mcp/tsconfig.json added (Phase 1)
• build/typecheck scripts updated to a real tsc compile, not node --check
• CLI still runs identically post-build (loopover-mcp --help/--version and its real
  commands behave unchanged)

Test Coverage Requirements

No behavior change from this migration alone. Existing tests must continue to pass unmodified.

Expected Outcome

packages/loopover-mcp's source is real, compiler-verified TypeScript instead of untyped plain JS.

Links & Resources

• chore(miner): migrate packages/loopover-miner from plain .js + hand-maintained .d.ts to real TypeScript #7290 -- the packages/loopover-miner equivalent of this same migration, same phasing pattern
• chore(mcp): add tsc build pipeline + convert small lib utilities to TypeScript (Phase 1 of #7291) #7328, chore(mcp): convert lib/local-branch.js to TypeScript (Phase 2 of #7291) #7329, chore(mcp): convert bin/loopover-mcp.js to TypeScript (Phase 3 of #7291) #7330 -- this issue's own phase sub-issues
• packages/loopover-engine/src/** -- the proven TypeScript precedent in this monorepo

[linear-code]

JSO-5095