Adds the three signal columns motivated by the manual keystroke
analysis in DEBT-036 directly to the SessionProfile table. Pre-v1 so
we modify the schema in place — Alembic arrives at v1.
Columns:
- kd_top_bigrams (TEXT) — JSON of top-N most-common digraphs with
mean IAT per bigram. Complements kd_digraph_simhash ("same typist?")
with "same typist in same mental state?" (tired / rested / distracted
shifts bigram-specific IATs measurably).
- kd_start_of_action_latency (REAL/DOUBLE) — median IAT of the first
keystroke after an idle gap > 1s. Separates "initiating a command"
from "executing a remembered one"; real humans have measurable
start-of-action latency, bots don't.
- kd_pause_hist_burst / _think / _distracted (INT) — three-bucket
histogram (counts, <0.2s / 0.2-1.5s / >1.5s). More discriminating
than the existing flat burst_ratio / think_ratio pair: C2 operators
concentrate in burst with a thin tail; opportunistic humans have a
fat think bucket and a long distracted tail.
Both backends get an idempotent ADD COLUMN migration
(_migrate_session_profile_table) wired into initialize() alongside
the existing _migrate_attackers_table path — guards on PRAGMA
table_info (SQLite) / information_schema.COLUMNS (MySQL) so reruns
are safe.
PII discipline comment on kd_digraph_simhash and kd_top_bigrams:
both operate on bigram CHARACTERS, never on raw input stream content.
Attacker passwords typed over SSH must not land here.
Test updated for the MySQL initialize() migration-order contract.
anti
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