secret redaction rewrites node names, which are part of the merge key #1754

Summary

Secret redaction is applied to every string property of every node, including name. name is
part of the merge key, so a redacted name does not just hide a symbol — it changes the node's
identity.

In one graph of 240 repositories, indexed with REDACT_SECRETS=true, 448 nodes are literally
named [REDACTED]:

Why a name trips the scanner at all

is_likely_secret calls a string a secret when it is at least 16 characters, contains one of ten
common words (key, secret, token, password, passwd, pwd, credential, auth,
private, access) and scores 3.8 bits of Shannon entropy. A method called
getAccessTokenForUser meets all three: it is long enough, it contains access and token, and
ordinary mixed-case identifiers sit well above 3.8 bits. Roughly 120 of 7,042 Java name
properties in our sample trip it.

Why it matters more than a hidden name

writer.py merges most labels on a key that includes name
(MERGE (n:Class {name: row.name, path: …, line_number: …})), so two different symbols whose
names were both redacted in the same file and line region can meet on one node. Module is worse:
_NAME_ONLY_MERGE_LABELS merges it on name alone, so every redacted module name in the whole
graph collapses onto a single node.

The downstream effects are quiet. Name-based call and inheritance resolution cannot match a symbol
whose name is the redaction marker, and the full-text index over name, source and docstring
cannot find it either, so queries return nothing rather than something wrong.

Suggestion

Identifiers are not values. The cheapest fix is to exclude the identity properties — name,
full_name and anything else that participates in a merge key — from the scan, and keep
redaction for the properties that carry user content (source, docstring, value). A stricter
alternative is to scan them but never allow a redaction to change a merge key, falling back to
storing the original name and recording a finding instead.

I am happy to send a patch for whichever shape you prefer.

Found while working on a separate over-redaction defect in the same function, reported with a fix
in #1753; this one is independent of that change and is not addressed by it.

Disclosure: this report was prepared with AI assistance (Claude Code) and reviewed by a human
before posting.