docs: add Six Sigma Agent, AgileCoder, Reflexion citations to taxonomy paper

Incorporate findings from literature survey: Six Sigma Agent (arXiv:2601.22290)
as the only prior explicit PM/OM-named framework, AgileCoder for Scrum sprints,
Reflexion as implicit PDCA, CAMEL for role theory.

paper/taxonomy.tex

@@ -141,6 +141,11 @@ sequential phases (design, coding, testing, documentation). Despite the
 ``company'' framing, the execution model is a \emph{linear pipeline} with
 pair-programming-style chat between adjacent roles.
 
+\textbf{AgileCoder} \citep{nguyen2024agilecoder} is the first framework to
+explicitly adopt sprint-based iteration, assigning Scrum Master and Product
+Manager roles to LLM agents with a Dynamic Code Graph Generator tracking
+inter-file dependencies between sprints.
+
 \textbf{CrewAI} organizes agents into ``crews'' with a ``manager'' agent
 orchestrating task delegation---an implicit \emph{hierarchical management}
 model with single-point-of-failure coordination.
@@ -150,6 +155,16 @@ framework where agents negotiate through multi-turn dialogue. The implicit
 model is \emph{committee decision-making}---all agents see all messages,
 consensus emerges through discussion.
 
+\textbf{The Six Sigma Agent} \citep{patel2026sixsigma} decomposes tasks
+into atomic dependency trees, executes each node $n$ times with independent
+LLM samples, and uses consensus voting to achieve defect rates scaling as
+$O(p^{\lceil n/2 \rceil})$---reaching 3.4 DPMO (the Six Sigma threshold)
+at $n=13$.
+
+\textbf{Reflexion} \citep{shinn2023reflexion} implements a de facto PDCA
+loop through verbal reinforcement: Plan $\to$ Act $\to$ Evaluate (Check)
+$\to$ Reflect (Act), though it does not name this structure explicitly.
+
 \textbf{ArcheFlow} \citep{nennemann2026archeflow} explicitly applies PDCA
 quality cycles with Jungian archetypal roles, representing the first
 framework to deliberately adopt a named PM/OM methodology with formal
@@ -158,11 +173,17 @@ convergence criteria.
 \subsection{The Gap}
 
 Despite the variety of frameworks, the PM/OM methods actually employed
-cluster tightly around three approaches: (1) waterfall-style sequential
-phases, (2) role-based team simulation, and (3) informal ``manager''
-delegation. Methods from lean manufacturing, statistical process control,
-military decision-making, innovation management, and constraint theory
-remain entirely unexplored in the agent orchestration literature.
+cluster tightly around four approaches: (1) waterfall-style sequential
+phases (MetaGPT, ChatDev), (2) role-based team simulation (CAMEL
+\citep{li2023camel}, CrewAI), (3) informal ``manager'' delegation
+(AutoGen), and (4) agile sprints (AgileCoder). The Six Sigma Agent
+\citep{patel2026sixsigma} is a notable exception---the only framework to
+explicitly name a PM/OM method as its primary architectural contribution.
+
+Methods from lean manufacturing, constraint theory, military
+decision-making, innovation management, and failure analysis remain
+unexplored in the peer-reviewed agent orchestration literature, despite
+strong structural compatibility with agent constraints.
 
 % ============================================================
 \section{Taxonomy of PM/OM Methods}