fix(chart,engine): rename PROTECTOR_FALCO_ADDR -> PROTECTOR_BEHAVIOR_ADDR, drop compat fallback

[thejefflarson]

Summary

Falco-retirement cleanup (ADR-0014's addenda). The engine already preferred
PROTECTOR_BEHAVIOR_ADDR and fell back to PROTECTOR_FALCO_ADDR (compat added in a
prior release). This PR migrates the in-repo chart to the new name and drops the
now-unneeded fallback:

• charts/protector/templates/deployment.yaml — renames the PROTECTOR_FALCO_ADDR env
  to PROTECTOR_BEHAVIOR_ADDR; the container port name falco-ingest → behavior-ingest.
• charts/protector/values.yaml — renames engine.falco.* → engine.ingest.*.
• charts/protector/templates/engine-services.yaml — renames the
  …-falco-ingest Service → …-behavior-ingest.
• charts/protector/templates/agent-daemonset.yaml — updates the agent's
  PROTECTOR_AGENT_ENDPOINT to point at the renamed Service/port.
• charts/protector/README.md, root README.md — doc updates to match.
• docs/adr/0014-behavioral-telemetry-ebpf.md — appends an addendum recording the
  fallback removal (in the ADR's existing addendum convention).
• engine/src/main.rs — drops the .or_else(|_| env::var("PROTECTOR_FALCO_ADDR"))
  compat fallback; the engine now reads only PROTECTOR_BEHAVIOR_ADDR.

The ingestAuth Secret + bearer-token mechanism (the agent presents it) is
unchanged — only the address/service naming moves.

Scope boundary — NOT included here

• The ../cluster fork is untouched. The deployed cluster runs a diverged fork of
  this chart that still sets PROTECTOR_FALCO_ADDR. Porting the rename there, and
  sequencing the deploy so the fork sets PROTECTOR_BEHAVIOR_ADDR and syncs before
  this fallback-dropped engine rolls (otherwise ingest breaks), is a required separate
  step — flagging it for the orchestrator/main loop, not done here.
• The actual Falco DaemonSet removal (separate, human, infra-repo change) is untouched.

How I tested it

• helm lint charts/protector — clean.
• helm template charts/protector (default values, and with agent.enabled=true) —
  confirmed the rendered manifest contains PROTECTOR_BEHAVIOR_ADDR and the
  …-behavior-ingest Service/port, and no PROTECTOR_FALCO_ADDR /
  …-falco-ingest anywhere in the output.
• Confirmed the ingestAuth Secret (…-ingest-auth) and
  PROTECTOR_INGEST_TOKEN_FILE wiring still render unchanged.
• cargo fmt -- --check, cargo clippy --all-targets -- -D warnings, cargo test
  (engine) — all clean/green (1225+10+9+3+1+1 tests passed, 2 ignored).
• No new unit test was added for the fallback removal specifically: the address
  resolution is a few inline env::var calls inside run() (the binary's async
  entrypoint), not an isolated function — matching this file's existing pattern where
  the other trivial env-parsing helpers (env_or, env_parse) are likewise untested
  in isolation. Removing the fallback branch is a straight subtraction of a
  no-longer-needed code path; cargo test confirms nothing else regressed.

Closes JEF-327