the pre-check phase entry is keyed wrong and its test cannot fail

[haribo]

What happens

removedPhases maps a retired phase name to an actionable message. Its first key is
"check" — a valid phase — with the message "folded into check (ADR-0035); rename
the phase". The key should be "pre-check", the name that was folded.

Probed against the parser:

written	result
check	parses — phaseNames is consulted first (def_parser.go:78), so the entry is unreachable
pre-check	expected a phase, got "pre-check" — the generic message, not the actionable one
post	phase "post": removed (ADR-0035)… — correct
banana	expected a phase, got "banana"

So the entry is dead code that also fails to do its job: the one name it was written for
gets the message every unknown word gets.

The test is green for the wrong reason

TestPhases_RemovedNamesRefused (internal/lang/control_test.go) asserts:

"pre-check": "check",
…
if !strings.Contains(err.Error(), want) {

pre-check contains check, so strings.Contains is satisfied by the generic message
expected a phase, got "pre-check". The test would pass with no removedPhases entry at
all — which is exactly the state it is in.

That is the sharper half of this issue: a substring assertion that cannot fail.

Build

• Key the entry "pre-check".
• Make the test assert something the generic message cannot satisfy — the distinctive part
  of the actionable text (rename the phase, ADR-0035), not a fragment of the input.
• While there: post's case is correct and its assertion has the same weakness
  ("removed" appears only in the actionable message, so it happens to hold — check it
  rather than assume it).

Validation

• pre-check produces the actionable message, asserted on a substring that appears only
  in it.
• The four surviving phases still parse.
• The corrected test fails when the removedPhases entry is removed — verify by removing
  it once, rather than trusting that it would.