test(review): cover the src/ linked-issue-hard-rules-config normalizer branches (62.50% branch coverage)

[JSONbored]

Context

src/review/linked-issue-hard-rules-config.ts is a byte-identical "twin" of the canonical
packages/loopover-engine/src/review/linked-issue-hard-rules-config.ts (they differ only in the
types import path — a deliberate directory-scanned parity pair, same pattern as the recent
#5779/#4879 engine extractions). The engine copy has full branch coverage via
test/unit/linked-issue-hard-rules-config-engine.test.ts, but the src/ twin's own test
(test/unit/linked-issue-hard-rules.test.ts) only exercises a subset of its normalizer branches,
leaving several src/-side branches never taken by any test that imports from ../../src/review/linked-issue-hard-rules-config. A local unsharded npm run test:coverage run confirms the file sits at
62.50% branch coverage (20/32).

Specifically untested branches in the src/ copy (functions normalizeMode, normalizeBoolean,
normalizeCloseDelaySeconds, normalizeStringList, normalizeLinkedIssueHardRulesConfig):

• normalizeMode (line 44-49): the value === undefined branch (return the field default) and the
  invalid-string branch (push a warning, fall back to default) are never hit — the existing test only
  passes a valid mode ("block") for one field.
• normalizeBoolean (line 51-56): both the undefined branch and the wrong-type branch (e.g. a
  string/number instead of boolean) are untested.
• normalizeCloseDelaySeconds (line 58-65): the undefined branch, the invalid-value branch
  (negative / NaN / non-number → warning + DEFAULT_CLOSE_DELAY_SECONDS), and the valid-but-clamped
  branch (Math.min(MAX_CLOSE_DELAY_SECONDS, Math.floor(value))) are all untested against the src/
  export.
• normalizeLinkedIssueHardRulesConfig (line 67-68): the top-level input === undefined branch is
  untested.

Because this is a scored src/** file, any future PR that legitimately touches one of these
functions inherits the 99% Codecov patch gate on lines it didn't even mean to change — closing this
gap now removes that latent trap.

Requirements

Add test cases to test/unit/linked-issue-hard-rules.test.ts (import stays
from "../../src/review/linked-issue-hard-rules-config") that exercise, for the src/ export
specifically:

1. normalizeLinkedIssueHardRulesConfig(undefined, warnings) returns the all-off default.
2. A mode field given an invalid string (e.g. "sometimes") falls back to its default and pushes a
   warning naming the field.
3. A mode field omitted (undefined) resolves to its own default (not just tested implicitly via the
   top-level default case).
4. defaultLabelRepo / verifyBeforeClose each get a non-boolean value (falls back + warns) and an
   omitted value (falls back to default silently).
5. closeDelaySeconds: omitted (default 30), negative (warns, falls back to 30), NaN (warns, falls
   back to 30), a fractional value under the cap (floors it), and a value above
   MAX_CLOSE_DELAY_SECONDS (clamps to 300).

Deliverables

• New/expanded it(...) blocks in test/unit/linked-issue-hard-rules.test.ts covering the five
  requirement groups above, each asserting both the returned value and the pushed warning text
  where applicable.

Test Coverage Requirements

This repo's Codecov codecov/patch gate is 99%+ branch-counted and hard on every changed line. Since
this issue's fix only adds test file lines (not src/** lines), it owes no new patch coverage
itself — but it should bring src/review/linked-issue-hard-rules-config.ts's own branch coverage from
62.50% to 100%, matching its engine twin.

Expected Outcome

src/review/linked-issue-hard-rules-config.ts reaches (or is verified to already effectively reach,
once these cases are added) 100% branch coverage, so the src/ twin's test suite is no longer
silently thinner than its packages/loopover-engine counterpart.

Links & Resources

• src/review/linked-issue-hard-rules-config.ts
• packages/loopover-engine/src/review/linked-issue-hard-rules-config.ts (fully-covered twin, use its
  test file test/unit/linked-issue-hard-rules-config-engine.test.ts as the pattern to mirror)
• test/unit/linked-issue-hard-rules.test.ts (file to extend)

[linear-code]

JSO-4032