[jacklanchantin]

Follow-up to #115 (these changes landed on the branch after it was merged).

• Fig. 2 caption label: "HackBench:" -> "HackBench." (matches Fig. 1).
• Sentence-case bold paragraph labels with trailing periods: "Reward hacking.", "Injecting synthetic hacks.", "Collecting natural hacks.", "Autoresearch agents.", "Results and findings.".
• Spell out "five"/"seven" tasks to match "one … task" and "eight chunks".
• Straight apostrophe in "monitor's" (Table 3 caption).
• Define s_0 (initial state) and env_T (final environment state) in the problem formulation.

[jacklanchantin]

Moved into #116.