release: deno task bump <version>; the warnings name the fix

[taras]

Motivation

The release warnings merged in #93 diagnose a forgotten version bump but leave
the fix to the reader — and the bump itself is ten hand-edited manifest
fields. The warnings should prescribe a single command.

Approach

• deno task bump <version>: scripts/bump-version.ts (Effection style)
  stamps the version field of every @executablemd member's deno.json and
  package.json, validates the semver argument, and fails loudly if a
  manifest has no version field. Formatting is preserved (string replace, not
  reserialization).
• The draft banner and the preflight caution note now name the command: the
  banner says to run deno task bump <version> and merge before publishing;
  the caution names deno task bump <tag-version> for the refused tag.
• Spec §2's ritual references the task; scripts/bump-version.ts joins the
  release-config list in ReleaseSpecWarning.

Verified: bumping to a test version changes exactly the ten version lines and
nothing else (then reverted); a non-semver argument is rejected; typecheck,
lint, and the workflow scripts (bash -n) pass.

Scope confirmation

• All changed files relate to the stated purpose
• No drive-by refactors or "while I'm here" cleanups
• No formatting changes mixed with functional changes

New abstractions (if any)

None — one task script following the scripts/ conventions.

New dependencies (if any)

None.

New tests (if any)

None — verified functionally as described.

[github-actions]

PR #94: release: deno task bump ; the warnings name the fix

6 files, +73 / -5

Scope

🟡 PR mixes config and source changes.

Structural

🟡 2 console statements.

Slop

✅ Slop indicators look low.

Static Analysis

✅ Oxlint found no issues.

Correctness

No extraneous code patterns detected.